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href="#new-assertassertionerroroptions"><code>new assert.AssertionError(options)</code></a></li> 130</ul> 131</li> 132<li><span class="stability_1"><a href="#class-assertcalltracker">Class: <code>assert.CallTracker</code></a></span> 133<ul> 134<li><a href="#new-assertcalltracker"><code>new assert.CallTracker()</code></a></li> 135<li><a href="#trackercallsfn-exact"><code>tracker.calls([fn][, exact])</code></a></li> 136<li><a href="#trackergetcallsfn"><code>tracker.getCalls(fn)</code></a></li> 137<li><a href="#trackerreport"><code>tracker.report()</code></a></li> 138<li><a href="#trackerresetfn"><code>tracker.reset([fn])</code></a></li> 139<li><a href="#trackerverify"><code>tracker.verify()</code></a></li> 140</ul> 141</li> 142<li><a href="#assertvalue-message"><code>assert(value[, message])</code></a></li> 143<li><a href="#assertdeepequalactual-expected-message"><code>assert.deepEqual(actual, expected[, message])</code></a> 144<ul> 145<li><a href="#comparison-details">Comparison details</a></li> 146</ul> 147</li> 148<li><a href="#assertdeepstrictequalactual-expected-message"><code>assert.deepStrictEqual(actual, expected[, message])</code></a> 149<ul> 150<li><a href="#comparison-details_1">Comparison details</a></li> 151</ul> 152</li> 153<li><a href="#assertdoesnotmatchstring-regexp-message"><code>assert.doesNotMatch(string, regexp[, message])</code></a></li> 154<li><a href="#assertdoesnotrejectasyncfn-error-message"><code>assert.doesNotReject(asyncFn[, error][, message])</code></a></li> 155<li><a href="#assertdoesnotthrowfn-error-message"><code>assert.doesNotThrow(fn[, error][, message])</code></a></li> 156<li><a href="#assertequalactual-expected-message"><code>assert.equal(actual, expected[, message])</code></a></li> 157<li><a href="#assertfailmessage"><code>assert.fail([message])</code></a></li> 158<li><span class="stability_0"><a href="#assertfailactual-expected-message-operator-stackstartfn"><code>assert.fail(actual, expected[, message[, operator[, stackStartFn]]])</code></a></span></li> 159<li><a href="#assertiferrorvalue"><code>assert.ifError(value)</code></a></li> 160<li><a href="#assertmatchstring-regexp-message"><code>assert.match(string, regexp[, message])</code></a></li> 161<li><a href="#assertnotdeepequalactual-expected-message"><code>assert.notDeepEqual(actual, expected[, message])</code></a></li> 162<li><a href="#assertnotdeepstrictequalactual-expected-message"><code>assert.notDeepStrictEqual(actual, expected[, message])</code></a></li> 163<li><a href="#assertnotequalactual-expected-message"><code>assert.notEqual(actual, expected[, message])</code></a></li> 164<li><a href="#assertnotstrictequalactual-expected-message"><code>assert.notStrictEqual(actual, expected[, message])</code></a></li> 165<li><a href="#assertokvalue-message"><code>assert.ok(value[, message])</code></a></li> 166<li><a href="#assertrejectsasyncfn-error-message"><code>assert.rejects(asyncFn[, error][, message])</code></a></li> 167<li><a href="#assertstrictequalactual-expected-message"><code>assert.strictEqual(actual, expected[, message])</code></a></li> 168<li><a href="#assertthrowsfn-error-message"><code>assert.throws(fn[, error][, message])</code></a></li> 169</ul> 170</li> 171</ul></div></div> 172 </li> 173 174 175 <li class="picker-header"> 176 <a href="#"> 177 <span class="collapsed-arrow">►</span><span class="expanded-arrow">▼</span> 178 Index 179 </a> 180 181 <div class="picker"><ul> 182<li><a href="documentation.html" class="nav-documentation">About this documentation</a></li> 183<li><a href="synopsis.html" class="nav-synopsis">Usage and example</a></li> 184 185 <li> 186 <a href="index.html">Index</a> 187 </li> 188 </ul> 189 190<hr class="line"> 191<ul> 192<li><a href="assert.html" class="nav-assert active">Assertion testing</a></li> 193<li><a href="async_context.html" class="nav-async_context">Asynchronous context tracking</a></li> 194<li><a href="async_hooks.html" class="nav-async_hooks">Async hooks</a></li> 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href="https://nodejs.org/docs/latest-v15.x/api/assert.html">15.x</a></li> 272<li><a href="https://nodejs.org/docs/latest-v14.x/api/assert.html">14.x</a></li> 273<li><a href="https://nodejs.org/docs/latest-v13.x/api/assert.html">13.x</a></li> 274<li><a href="https://nodejs.org/docs/latest-v12.x/api/assert.html">12.x</a></li> 275<li><a href="https://nodejs.org/docs/latest-v11.x/api/assert.html">11.x</a></li> 276<li><a href="https://nodejs.org/docs/latest-v10.x/api/assert.html">10.x</a></li> 277<li><a href="https://nodejs.org/docs/latest-v9.x/api/assert.html">9.x</a></li> 278<li><a href="https://nodejs.org/docs/latest-v8.x/api/assert.html">8.x</a></li> 279<li><a href="https://nodejs.org/docs/latest-v7.x/api/assert.html">7.x</a></li> 280<li><a href="https://nodejs.org/docs/latest-v6.x/api/assert.html">6.x</a></li> 281<li><a href="https://nodejs.org/docs/latest-v5.x/api/assert.html">5.x</a></li> 282<li><a href="https://nodejs.org/docs/latest-v4.x/api/assert.html">4.x</a></li> 283<li><a href="https://nodejs.org/docs/latest-v0.12.x/api/assert.html">0.12.x</a></li> 284<li><a href="https://nodejs.org/docs/latest-v0.10.x/api/assert.html">0.10.x</a></li></ol></div> 285 </li> 286 287 <li class="picker-header"> 288 <a href="#"> 289 <span class="collapsed-arrow">►</span><span class="expanded-arrow">▼</span> 290 Options 291 </a> 292 293 <div class="picker"> 294 <ul> 295 <li> 296 <a href="all.html">View on single page</a> 297 </li> 298 <li> 299 <a href="assert.json">View as JSON</a> 300 </li> 301 <li class="edit_on_github"><a href="https://github.com/nodejs/node/edit/main/doc/api/assert.md">Edit on GitHub</a></li> 302 </ul> 303 </div> 304 </li> 305 </ul> 306 </div> 307 <hr> 308 </header> 309 310 <details id="toc" open><summary>Table of contents</summary><ul> 311<li><span class="stability_2"><a href="#assert">Assert</a></span> 312<ul> 313<li><a href="#strict-assertion-mode">Strict assertion mode</a></li> 314<li><a href="#legacy-assertion-mode">Legacy assertion mode</a></li> 315<li><a href="#class-assertassertionerror">Class: assert.AssertionError</a> 316<ul> 317<li><a href="#new-assertassertionerroroptions"><code>new assert.AssertionError(options)</code></a></li> 318</ul> 319</li> 320<li><span class="stability_1"><a href="#class-assertcalltracker">Class: <code>assert.CallTracker</code></a></span> 321<ul> 322<li><a href="#new-assertcalltracker"><code>new assert.CallTracker()</code></a></li> 323<li><a href="#trackercallsfn-exact"><code>tracker.calls([fn][, exact])</code></a></li> 324<li><a href="#trackergetcallsfn"><code>tracker.getCalls(fn)</code></a></li> 325<li><a href="#trackerreport"><code>tracker.report()</code></a></li> 326<li><a href="#trackerresetfn"><code>tracker.reset([fn])</code></a></li> 327<li><a href="#trackerverify"><code>tracker.verify()</code></a></li> 328</ul> 329</li> 330<li><a href="#assertvalue-message"><code>assert(value[, message])</code></a></li> 331<li><a href="#assertdeepequalactual-expected-message"><code>assert.deepEqual(actual, expected[, message])</code></a> 332<ul> 333<li><a href="#comparison-details">Comparison details</a></li> 334</ul> 335</li> 336<li><a href="#assertdeepstrictequalactual-expected-message"><code>assert.deepStrictEqual(actual, expected[, message])</code></a> 337<ul> 338<li><a href="#comparison-details_1">Comparison details</a></li> 339</ul> 340</li> 341<li><a href="#assertdoesnotmatchstring-regexp-message"><code>assert.doesNotMatch(string, regexp[, message])</code></a></li> 342<li><a href="#assertdoesnotrejectasyncfn-error-message"><code>assert.doesNotReject(asyncFn[, error][, message])</code></a></li> 343<li><a href="#assertdoesnotthrowfn-error-message"><code>assert.doesNotThrow(fn[, error][, message])</code></a></li> 344<li><a href="#assertequalactual-expected-message"><code>assert.equal(actual, expected[, message])</code></a></li> 345<li><a href="#assertfailmessage"><code>assert.fail([message])</code></a></li> 346<li><span class="stability_0"><a href="#assertfailactual-expected-message-operator-stackstartfn"><code>assert.fail(actual, expected[, message[, operator[, stackStartFn]]])</code></a></span></li> 347<li><a href="#assertiferrorvalue"><code>assert.ifError(value)</code></a></li> 348<li><a href="#assertmatchstring-regexp-message"><code>assert.match(string, regexp[, message])</code></a></li> 349<li><a href="#assertnotdeepequalactual-expected-message"><code>assert.notDeepEqual(actual, expected[, message])</code></a></li> 350<li><a href="#assertnotdeepstrictequalactual-expected-message"><code>assert.notDeepStrictEqual(actual, expected[, message])</code></a></li> 351<li><a href="#assertnotequalactual-expected-message"><code>assert.notEqual(actual, expected[, message])</code></a></li> 352<li><a href="#assertnotstrictequalactual-expected-message"><code>assert.notStrictEqual(actual, expected[, message])</code></a></li> 353<li><a href="#assertokvalue-message"><code>assert.ok(value[, message])</code></a></li> 354<li><a href="#assertrejectsasyncfn-error-message"><code>assert.rejects(asyncFn[, error][, message])</code></a></li> 355<li><a href="#assertstrictequalactual-expected-message"><code>assert.strictEqual(actual, expected[, message])</code></a></li> 356<li><a href="#assertthrowsfn-error-message"><code>assert.throws(fn[, error][, message])</code></a></li> 357</ul> 358</li> 359</ul></details> 360 361 <div id="apicontent"> 362 <h2>Assert<span><a class="mark" href="#assert" id="assert">#</a></span><a aria-hidden="true" class="legacy" id="assert_assert"></a></h2> 363 364<p></p><div class="api_stability api_stability_2"><a href="documentation.html#stability-index">Stability: 2</a> - Stable</div><p></p> 365<p><strong>Source Code:</strong> <a href="https://github.com/nodejs/node/blob/v18.20.1/lib/assert.js">lib/assert.js</a></p> 366<p>The <code>node:assert</code> module provides a set of assertion functions for verifying 367invariants.</p> 368<section><h3>Strict assertion mode<span><a class="mark" href="#strict-assertion-mode" id="strict-assertion-mode">#</a></span><a aria-hidden="true" class="legacy" id="assert_strict_assertion_mode"></a></h3> 369<div class="api_metadata"> 370<details class="changelog"><summary>History</summary> 371<table> 372<tbody><tr><th>Version</th><th>Changes</th></tr> 373<tr><td>v15.0.0</td> 374<td><p>Exposed as <code>require('node:assert/strict')</code>.</p></td></tr> 375<tr><td>v13.9.0, v12.16.2</td> 376<td><p>Changed "strict mode" to "strict assertion mode" and "legacy mode" to "legacy assertion mode" to avoid confusion with the more usual meaning of "strict mode".</p></td></tr> 377<tr><td>v9.9.0</td> 378<td><p>Added error diffs to the strict assertion mode.</p></td></tr> 379<tr><td>v9.9.0</td> 380<td><p>Added strict assertion mode to the assert module.</p></td></tr> 381<tr><td>v9.9.0</td> 382<td><p><span>Added in: v9.9.0</span></p></td></tr> 383</tbody></table> 384</details> 385</div> 386<p>In strict assertion mode, non-strict methods behave like their corresponding 387strict methods. For example, <a href="#assertdeepequalactual-expected-message"><code>assert.deepEqual()</code></a> will behave like 388<a href="#assertdeepstrictequalactual-expected-message"><code>assert.deepStrictEqual()</code></a>.</p> 389<p>In strict assertion mode, error messages for objects display a diff. In legacy 390assertion mode, error messages for objects display the objects, often truncated.</p> 391<p>To use strict assertion mode:</p> 392 393<pre class="with-47-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> { strict <span class="hljs-keyword">as</span> assert } <span class="hljs-keyword">from</span> <span class="hljs-string">'node:assert'</span>;</code><code class="language-js cjs"><span class="hljs-keyword">const</span> assert = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:assert'</span>).<span class="hljs-property">strict</span>;</code><button class="copy-button">copy</button></pre> 394 395<pre class="with-45-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> assert <span class="hljs-keyword">from</span> <span class="hljs-string">'node:assert/strict'</span>;</code><code class="language-js cjs"><span class="hljs-keyword">const</span> assert = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:assert/strict'</span>);</code><button class="copy-button">copy</button></pre> 396<p>Example error diff:</p> 397 398<pre class="with-47-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> { strict <span class="hljs-keyword">as</span> assert } <span class="hljs-keyword">from</span> <span class="hljs-string">'node:assert'</span>; 399 400assert.<span class="hljs-title function_">deepEqual</span>([[[<span class="hljs-number">1</span>, <span class="hljs-number">2</span>, <span class="hljs-number">3</span>]], <span class="hljs-number">4</span>, <span class="hljs-number">5</span>], [[[<span class="hljs-number">1</span>, <span class="hljs-number">2</span>, <span class="hljs-string">'3'</span>]], <span class="hljs-number">4</span>, <span class="hljs-number">5</span>]); 401<span class="hljs-comment">// AssertionError: Expected inputs to be strictly deep-equal:</span> 402<span class="hljs-comment">// + actual - expected ... Lines skipped</span> 403<span class="hljs-comment">//</span> 404<span class="hljs-comment">// [</span> 405<span class="hljs-comment">// [</span> 406<span class="hljs-comment">// ...</span> 407<span class="hljs-comment">// 2,</span> 408<span class="hljs-comment">// + 3</span> 409<span class="hljs-comment">// - '3'</span> 410<span class="hljs-comment">// ],</span> 411<span class="hljs-comment">// ...</span> 412<span class="hljs-comment">// 5</span> 413<span class="hljs-comment">// ]</span></code><code class="language-js cjs"><span class="hljs-keyword">const</span> assert = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:assert/strict'</span>); 414 415assert.<span class="hljs-title function_">deepEqual</span>([[[<span class="hljs-number">1</span>, <span class="hljs-number">2</span>, <span class="hljs-number">3</span>]], <span class="hljs-number">4</span>, <span class="hljs-number">5</span>], [[[<span class="hljs-number">1</span>, <span class="hljs-number">2</span>, <span class="hljs-string">'3'</span>]], <span class="hljs-number">4</span>, <span class="hljs-number">5</span>]); 416<span class="hljs-comment">// AssertionError: Expected inputs to be strictly deep-equal:</span> 417<span class="hljs-comment">// + actual - expected ... Lines skipped</span> 418<span class="hljs-comment">//</span> 419<span class="hljs-comment">// [</span> 420<span class="hljs-comment">// [</span> 421<span class="hljs-comment">// ...</span> 422<span class="hljs-comment">// 2,</span> 423<span class="hljs-comment">// + 3</span> 424<span class="hljs-comment">// - '3'</span> 425<span class="hljs-comment">// ],</span> 426<span class="hljs-comment">// ...</span> 427<span class="hljs-comment">// 5</span> 428<span class="hljs-comment">// ]</span></code><button class="copy-button">copy</button></pre> 429<p>To deactivate the colors, use the <code>NO_COLOR</code> or <code>NODE_DISABLE_COLORS</code> 430environment variables. This will also deactivate the colors in the REPL. For 431more on color support in terminal environments, read the tty 432<a href="tty.html#writestreamgetcolordepthenv"><code>getColorDepth()</code></a> documentation.</p> 433</section><section><h3>Legacy assertion mode<span><a class="mark" href="#legacy-assertion-mode" id="legacy-assertion-mode">#</a></span><a aria-hidden="true" class="legacy" id="assert_legacy_assertion_mode"></a></h3> 434<p>Legacy assertion mode uses the <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Equality"><code>==</code> operator</a> in:</p> 435<ul> 436<li><a href="#assertdeepequalactual-expected-message"><code>assert.deepEqual()</code></a></li> 437<li><a href="#assertequalactual-expected-message"><code>assert.equal()</code></a></li> 438<li><a href="#assertnotdeepequalactual-expected-message"><code>assert.notDeepEqual()</code></a></li> 439<li><a href="#assertnotequalactual-expected-message"><code>assert.notEqual()</code></a></li> 440</ul> 441<p>To use legacy assertion mode:</p> 442 443<pre class="with-38-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> assert <span class="hljs-keyword">from</span> <span class="hljs-string">'node:assert'</span>;</code><code class="language-js cjs"><span class="hljs-keyword">const</span> assert = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:assert'</span>);</code><button class="copy-button">copy</button></pre> 444<p>Legacy assertion mode may have surprising results, especially when using 445<a href="#assertdeepequalactual-expected-message"><code>assert.deepEqual()</code></a>:</p> 446<pre><code class="language-js cjs"><span class="hljs-comment">// WARNING: This does not throw an AssertionError in legacy assertion mode!</span> 447assert.<span class="hljs-title function_">deepEqual</span>(<span class="hljs-regexp">/a/gi</span>, <span class="hljs-keyword">new</span> <span class="hljs-title class_">Date</span>());</code> <button class="copy-button">copy</button></pre> 448</section><section><h3>Class: assert.AssertionError<a class="srclink" href="https://github.com/nodejs/node/blob/1d526a47af29d59ad196c4e05606b0ec6f8090d9/lib/assert.js#L178">[src]</a><span><a class="mark" href="#class-assertassertionerror" id="class-assertassertionerror">#</a></span><a aria-hidden="true" class="legacy" id="assert_class_assert_assertionerror"></a></h3> 449<ul> 450<li>Extends: <a href="errors.html#class-error" class="type"><errors.Error></a></li> 451</ul> 452<p>Indicates the failure of an assertion. All errors thrown by the <code>node:assert</code> 453module will be instances of the <code>AssertionError</code> class.</p> 454<h4><code>new assert.AssertionError(options)</code><span><a class="mark" href="#new-assertassertionerroroptions" id="new-assertassertionerroroptions">#</a></span><a aria-hidden="true" class="legacy" id="assert_new_assert_assertionerror_options"></a></h4> 455<div class="api_metadata"> 456<span>Added in: v0.1.21</span> 457</div> 458<ul> 459<li><code>options</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> 460<ul> 461<li><code>message</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> If provided, the error message is set to this value.</li> 462<li><code>actual</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a> The <code>actual</code> property on the error instance.</li> 463<li><code>expected</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a> The <code>expected</code> property on the error instance.</li> 464<li><code>operator</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> The <code>operator</code> property on the error instance.</li> 465<li><code>stackStartFn</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> If provided, the generated stack trace omits 466frames before this function.</li> 467</ul> 468</li> 469</ul> 470<p>A subclass of <code>Error</code> that indicates the failure of an assertion.</p> 471<p>All instances contain the built-in <code>Error</code> properties (<code>message</code> and <code>name</code>) 472and:</p> 473<ul> 474<li><code>actual</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a> Set to the <code>actual</code> argument for methods such as 475<a href="#assertstrictequalactual-expected-message"><code>assert.strictEqual()</code></a>.</li> 476<li><code>expected</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a> Set to the <code>expected</code> value for methods such as 477<a href="#assertstrictequalactual-expected-message"><code>assert.strictEqual()</code></a>.</li> 478<li><code>generatedMessage</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> Indicates if the message was auto-generated 479(<code>true</code>) or not.</li> 480<li><code>code</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> Value is always <code>ERR_ASSERTION</code> to show that the error is an 481assertion error.</li> 482<li><code>operator</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> Set to the passed in operator value.</li> 483</ul> 484 485<pre class="with-38-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> assert <span class="hljs-keyword">from</span> <span class="hljs-string">'node:assert'</span>; 486 487<span class="hljs-comment">// Generate an AssertionError to compare the error message later:</span> 488<span class="hljs-keyword">const</span> { message } = <span class="hljs-keyword">new</span> assert.<span class="hljs-title class_">AssertionError</span>({ 489 <span class="hljs-attr">actual</span>: <span class="hljs-number">1</span>, 490 <span class="hljs-attr">expected</span>: <span class="hljs-number">2</span>, 491 <span class="hljs-attr">operator</span>: <span class="hljs-string">'strictEqual'</span>, 492}); 493 494<span class="hljs-comment">// Verify error output:</span> 495<span class="hljs-keyword">try</span> { 496 assert.<span class="hljs-title function_">strictEqual</span>(<span class="hljs-number">1</span>, <span class="hljs-number">2</span>); 497} <span class="hljs-keyword">catch</span> (err) { 498 <span class="hljs-title function_">assert</span>(err <span class="hljs-keyword">instanceof</span> assert.<span class="hljs-property">AssertionError</span>); 499 assert.<span class="hljs-title function_">strictEqual</span>(err.<span class="hljs-property">message</span>, message); 500 assert.<span class="hljs-title function_">strictEqual</span>(err.<span class="hljs-property">name</span>, <span class="hljs-string">'AssertionError'</span>); 501 assert.<span class="hljs-title function_">strictEqual</span>(err.<span class="hljs-property">actual</span>, <span class="hljs-number">1</span>); 502 assert.<span class="hljs-title function_">strictEqual</span>(err.<span class="hljs-property">expected</span>, <span class="hljs-number">2</span>); 503 assert.<span class="hljs-title function_">strictEqual</span>(err.<span class="hljs-property">code</span>, <span class="hljs-string">'ERR_ASSERTION'</span>); 504 assert.<span class="hljs-title function_">strictEqual</span>(err.<span class="hljs-property">operator</span>, <span class="hljs-string">'strictEqual'</span>); 505 assert.<span class="hljs-title function_">strictEqual</span>(err.<span class="hljs-property">generatedMessage</span>, <span class="hljs-literal">true</span>); 506}</code><code class="language-js cjs"><span class="hljs-keyword">const</span> assert = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:assert'</span>); 507 508<span class="hljs-comment">// Generate an AssertionError to compare the error message later:</span> 509<span class="hljs-keyword">const</span> { message } = <span class="hljs-keyword">new</span> assert.<span class="hljs-title class_">AssertionError</span>({ 510 <span class="hljs-attr">actual</span>: <span class="hljs-number">1</span>, 511 <span class="hljs-attr">expected</span>: <span class="hljs-number">2</span>, 512 <span class="hljs-attr">operator</span>: <span class="hljs-string">'strictEqual'</span>, 513}); 514 515<span class="hljs-comment">// Verify error output:</span> 516<span class="hljs-keyword">try</span> { 517 assert.<span class="hljs-title function_">strictEqual</span>(<span class="hljs-number">1</span>, <span class="hljs-number">2</span>); 518} <span class="hljs-keyword">catch</span> (err) { 519 <span class="hljs-title function_">assert</span>(err <span class="hljs-keyword">instanceof</span> assert.<span class="hljs-property">AssertionError</span>); 520 assert.<span class="hljs-title function_">strictEqual</span>(err.<span class="hljs-property">message</span>, message); 521 assert.<span class="hljs-title function_">strictEqual</span>(err.<span class="hljs-property">name</span>, <span class="hljs-string">'AssertionError'</span>); 522 assert.<span class="hljs-title function_">strictEqual</span>(err.<span class="hljs-property">actual</span>, <span class="hljs-number">1</span>); 523 assert.<span class="hljs-title function_">strictEqual</span>(err.<span class="hljs-property">expected</span>, <span class="hljs-number">2</span>); 524 assert.<span class="hljs-title function_">strictEqual</span>(err.<span class="hljs-property">code</span>, <span class="hljs-string">'ERR_ASSERTION'</span>); 525 assert.<span class="hljs-title function_">strictEqual</span>(err.<span class="hljs-property">operator</span>, <span class="hljs-string">'strictEqual'</span>); 526 assert.<span class="hljs-title function_">strictEqual</span>(err.<span class="hljs-property">generatedMessage</span>, <span class="hljs-literal">true</span>); 527}</code><button class="copy-button">copy</button></pre> 528</section><section><h3>Class: <code>assert.CallTracker</code><span><a class="mark" href="#class-assertcalltracker" id="class-assertcalltracker">#</a></span><a aria-hidden="true" class="legacy" id="assert_class_assert_calltracker"></a></h3> 529<div class="api_metadata"> 530<span>Added in: v14.2.0, v12.19.0</span> 531</div> 532<p></p><div class="api_stability api_stability_1"><a href="documentation.html#stability-index">Stability: 1</a> - Experimental</div><p></p> 533<p>This feature is currently experimental and behavior might still change.</p> 534<h4><code>new assert.CallTracker()</code><span><a class="mark" href="#new-assertcalltracker" id="new-assertcalltracker">#</a></span><a aria-hidden="true" class="legacy" id="assert_new_assert_calltracker"></a></h4> 535<div class="api_metadata"> 536<span>Added in: v14.2.0, v12.19.0</span> 537</div> 538<p>Creates a new <a href="#class-assertcalltracker"><code>CallTracker</code></a> object which can be used to track if functions 539were called a specific number of times. The <code>tracker.verify()</code> must be called 540for the verification to take place. The usual pattern would be to call it in a 541<a href="process.html#event-exit"><code>process.on('exit')</code></a> handler.</p> 542 543<pre class="with-38-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> assert <span class="hljs-keyword">from</span> <span class="hljs-string">'node:assert'</span>; 544<span class="hljs-keyword">import</span> process <span class="hljs-keyword">from</span> <span class="hljs-string">'node:process'</span>; 545 546<span class="hljs-keyword">const</span> tracker = <span class="hljs-keyword">new</span> assert.<span class="hljs-title class_">CallTracker</span>(); 547 548<span class="hljs-keyword">function</span> <span class="hljs-title function_">func</span>(<span class="hljs-params"></span>) {} 549 550<span class="hljs-comment">// callsfunc() must be called exactly 1 time before tracker.verify().</span> 551<span class="hljs-keyword">const</span> callsfunc = tracker.<span class="hljs-title function_">calls</span>(func, <span class="hljs-number">1</span>); 552 553<span class="hljs-title function_">callsfunc</span>(); 554 555<span class="hljs-comment">// Calls tracker.verify() and verifies if all tracker.calls() functions have</span> 556<span class="hljs-comment">// been called exact times.</span> 557process.<span class="hljs-title function_">on</span>(<span class="hljs-string">'exit'</span>, <span class="hljs-function">() =></span> { 558 tracker.<span class="hljs-title function_">verify</span>(); 559});</code><code class="language-js cjs"><span class="hljs-keyword">const</span> assert = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:assert'</span>); 560 561<span class="hljs-keyword">const</span> tracker = <span class="hljs-keyword">new</span> assert.<span class="hljs-title class_">CallTracker</span>(); 562 563<span class="hljs-keyword">function</span> <span class="hljs-title function_">func</span>(<span class="hljs-params"></span>) {} 564 565<span class="hljs-comment">// callsfunc() must be called exactly 1 time before tracker.verify().</span> 566<span class="hljs-keyword">const</span> callsfunc = tracker.<span class="hljs-title function_">calls</span>(func, <span class="hljs-number">1</span>); 567 568<span class="hljs-title function_">callsfunc</span>(); 569 570<span class="hljs-comment">// Calls tracker.verify() and verifies if all tracker.calls() functions have</span> 571<span class="hljs-comment">// been called exact times.</span> 572process.<span class="hljs-title function_">on</span>(<span class="hljs-string">'exit'</span>, <span class="hljs-function">() =></span> { 573 tracker.<span class="hljs-title function_">verify</span>(); 574});</code><button class="copy-button">copy</button></pre> 575<h4><code>tracker.calls([fn][, exact])</code><span><a class="mark" href="#trackercallsfn-exact" id="trackercallsfn-exact">#</a></span><a aria-hidden="true" class="legacy" id="assert_tracker_calls_fn_exact"></a></h4> 576<div class="api_metadata"> 577<span>Added in: v14.2.0, v12.19.0</span> 578</div> 579<ul> 580<li><code>fn</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> <strong>Default:</strong> A no-op function.</li> 581<li><code>exact</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> <strong>Default:</strong> <code>1</code>.</li> 582<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> that wraps <code>fn</code>.</li> 583</ul> 584<p>The wrapper function is expected to be called exactly <code>exact</code> times. If the 585function has not been called exactly <code>exact</code> times when 586<a href="#trackerverify"><code>tracker.verify()</code></a> is called, then <a href="#trackerverify"><code>tracker.verify()</code></a> will throw an 587error.</p> 588 589<pre class="with-38-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> assert <span class="hljs-keyword">from</span> <span class="hljs-string">'node:assert'</span>; 590 591<span class="hljs-comment">// Creates call tracker.</span> 592<span class="hljs-keyword">const</span> tracker = <span class="hljs-keyword">new</span> assert.<span class="hljs-title class_">CallTracker</span>(); 593 594<span class="hljs-keyword">function</span> <span class="hljs-title function_">func</span>(<span class="hljs-params"></span>) {} 595 596<span class="hljs-comment">// Returns a function that wraps func() that must be called exact times</span> 597<span class="hljs-comment">// before tracker.verify().</span> 598<span class="hljs-keyword">const</span> callsfunc = tracker.<span class="hljs-title function_">calls</span>(func);</code><code class="language-js cjs"><span class="hljs-keyword">const</span> assert = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:assert'</span>); 599 600<span class="hljs-comment">// Creates call tracker.</span> 601<span class="hljs-keyword">const</span> tracker = <span class="hljs-keyword">new</span> assert.<span class="hljs-title class_">CallTracker</span>(); 602 603<span class="hljs-keyword">function</span> <span class="hljs-title function_">func</span>(<span class="hljs-params"></span>) {} 604 605<span class="hljs-comment">// Returns a function that wraps func() that must be called exact times</span> 606<span class="hljs-comment">// before tracker.verify().</span> 607<span class="hljs-keyword">const</span> callsfunc = tracker.<span class="hljs-title function_">calls</span>(func);</code><button class="copy-button">copy</button></pre> 608<h4><code>tracker.getCalls(fn)</code><span><a class="mark" href="#trackergetcallsfn" id="trackergetcallsfn">#</a></span><a aria-hidden="true" class="legacy" id="assert_tracker_getcalls_fn"></a></h4> 609<div class="api_metadata"> 610<span>Added in: v18.8.0</span> 611</div> 612<ul> 613<li> 614<p><code>fn</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a>.</p> 615</li> 616<li> 617<p>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array" class="type"><Array></a> with all the calls to a tracked function.</p> 618</li> 619<li> 620<p>Object <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a></p> 621<ul> 622<li><code>thisArg</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a></li> 623<li><code>arguments</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array" class="type"><Array></a> the arguments passed to the tracked function</li> 624</ul> 625</li> 626</ul> 627 628<pre class="with-38-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> assert <span class="hljs-keyword">from</span> <span class="hljs-string">'node:assert'</span>; 629 630<span class="hljs-keyword">const</span> tracker = <span class="hljs-keyword">new</span> assert.<span class="hljs-title class_">CallTracker</span>(); 631 632<span class="hljs-keyword">function</span> <span class="hljs-title function_">func</span>(<span class="hljs-params"></span>) {} 633<span class="hljs-keyword">const</span> callsfunc = tracker.<span class="hljs-title function_">calls</span>(func); 634<span class="hljs-title function_">callsfunc</span>(<span class="hljs-number">1</span>, <span class="hljs-number">2</span>, <span class="hljs-number">3</span>); 635 636assert.<span class="hljs-title function_">deepStrictEqual</span>(tracker.<span class="hljs-title function_">getCalls</span>(callsfunc), 637 [{ <span class="hljs-attr">thisArg</span>: <span class="hljs-literal">undefined</span>, <span class="hljs-attr">arguments</span>: [<span class="hljs-number">1</span>, <span class="hljs-number">2</span>, <span class="hljs-number">3</span>] }]);</code><code class="language-js cjs"><span class="hljs-keyword">const</span> assert = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:assert'</span>); 638 639<span class="hljs-comment">// Creates call tracker.</span> 640<span class="hljs-keyword">const</span> tracker = <span class="hljs-keyword">new</span> assert.<span class="hljs-title class_">CallTracker</span>(); 641 642<span class="hljs-keyword">function</span> <span class="hljs-title function_">func</span>(<span class="hljs-params"></span>) {} 643<span class="hljs-keyword">const</span> callsfunc = tracker.<span class="hljs-title function_">calls</span>(func); 644<span class="hljs-title function_">callsfunc</span>(<span class="hljs-number">1</span>, <span class="hljs-number">2</span>, <span class="hljs-number">3</span>); 645 646assert.<span class="hljs-title function_">deepStrictEqual</span>(tracker.<span class="hljs-title function_">getCalls</span>(callsfunc), 647 [{ <span class="hljs-attr">thisArg</span>: <span class="hljs-literal">undefined</span>, <span class="hljs-attr">arguments</span>: [<span class="hljs-number">1</span>, <span class="hljs-number">2</span>, <span class="hljs-number">3</span>] }]);</code><button class="copy-button">copy</button></pre> 648<h4><code>tracker.report()</code><span><a class="mark" href="#trackerreport" id="trackerreport">#</a></span><a aria-hidden="true" class="legacy" id="assert_tracker_report"></a></h4> 649<div class="api_metadata"> 650<span>Added in: v14.2.0, v12.19.0</span> 651</div> 652<ul> 653<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array" class="type"><Array></a> of objects containing information about the wrapper functions 654returned by <a href="#trackercallsfn-exact"><code>tracker.calls()</code></a>.</li> 655<li>Object <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> 656<ul> 657<li><code>message</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 658<li><code>actual</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> The actual number of times the function was called.</li> 659<li><code>expected</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> The number of times the function was expected to be 660called.</li> 661<li><code>operator</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> The name of the function that is wrapped.</li> 662<li><code>stack</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> A stack trace of the function.</li> 663</ul> 664</li> 665</ul> 666<p>The arrays contains information about the expected and actual number of calls of 667the functions that have not been called the expected number of times.</p> 668 669<pre class="with-38-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> assert <span class="hljs-keyword">from</span> <span class="hljs-string">'node:assert'</span>; 670 671<span class="hljs-comment">// Creates call tracker.</span> 672<span class="hljs-keyword">const</span> tracker = <span class="hljs-keyword">new</span> assert.<span class="hljs-title class_">CallTracker</span>(); 673 674<span class="hljs-keyword">function</span> <span class="hljs-title function_">func</span>(<span class="hljs-params"></span>) {} 675 676<span class="hljs-comment">// Returns a function that wraps func() that must be called exact times</span> 677<span class="hljs-comment">// before tracker.verify().</span> 678<span class="hljs-keyword">const</span> callsfunc = tracker.<span class="hljs-title function_">calls</span>(func, <span class="hljs-number">2</span>); 679 680<span class="hljs-comment">// Returns an array containing information on callsfunc()</span> 681<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(tracker.<span class="hljs-title function_">report</span>()); 682<span class="hljs-comment">// [</span> 683<span class="hljs-comment">// {</span> 684<span class="hljs-comment">// message: 'Expected the func function to be executed 2 time(s) but was</span> 685<span class="hljs-comment">// executed 0 time(s).',</span> 686<span class="hljs-comment">// actual: 0,</span> 687<span class="hljs-comment">// expected: 2,</span> 688<span class="hljs-comment">// operator: 'func',</span> 689<span class="hljs-comment">// stack: stack trace</span> 690<span class="hljs-comment">// }</span> 691<span class="hljs-comment">// ]</span></code><code class="language-js cjs"><span class="hljs-keyword">const</span> assert = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:assert'</span>); 692 693<span class="hljs-comment">// Creates call tracker.</span> 694<span class="hljs-keyword">const</span> tracker = <span class="hljs-keyword">new</span> assert.<span class="hljs-title class_">CallTracker</span>(); 695 696<span class="hljs-keyword">function</span> <span class="hljs-title function_">func</span>(<span class="hljs-params"></span>) {} 697 698<span class="hljs-comment">// Returns a function that wraps func() that must be called exact times</span> 699<span class="hljs-comment">// before tracker.verify().</span> 700<span class="hljs-keyword">const</span> callsfunc = tracker.<span class="hljs-title function_">calls</span>(func, <span class="hljs-number">2</span>); 701 702<span class="hljs-comment">// Returns an array containing information on callsfunc()</span> 703<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(tracker.<span class="hljs-title function_">report</span>()); 704<span class="hljs-comment">// [</span> 705<span class="hljs-comment">// {</span> 706<span class="hljs-comment">// message: 'Expected the func function to be executed 2 time(s) but was</span> 707<span class="hljs-comment">// executed 0 time(s).',</span> 708<span class="hljs-comment">// actual: 0,</span> 709<span class="hljs-comment">// expected: 2,</span> 710<span class="hljs-comment">// operator: 'func',</span> 711<span class="hljs-comment">// stack: stack trace</span> 712<span class="hljs-comment">// }</span> 713<span class="hljs-comment">// ]</span></code><button class="copy-button">copy</button></pre> 714<h4><code>tracker.reset([fn])</code><span><a class="mark" href="#trackerresetfn" id="trackerresetfn">#</a></span><a aria-hidden="true" class="legacy" id="assert_tracker_reset_fn"></a></h4> 715<div class="api_metadata"> 716<span>Added in: v18.8.0</span> 717</div> 718<ul> 719<li><code>fn</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> a tracked function to reset.</li> 720</ul> 721<p>Reset calls of the call tracker. 722If a tracked function is passed as an argument, the calls will be reset for it. 723If no arguments are passed, all tracked functions will be reset</p> 724 725<pre class="with-38-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> assert <span class="hljs-keyword">from</span> <span class="hljs-string">'node:assert'</span>; 726 727<span class="hljs-keyword">const</span> tracker = <span class="hljs-keyword">new</span> assert.<span class="hljs-title class_">CallTracker</span>(); 728 729<span class="hljs-keyword">function</span> <span class="hljs-title function_">func</span>(<span class="hljs-params"></span>) {} 730<span class="hljs-keyword">const</span> callsfunc = tracker.<span class="hljs-title function_">calls</span>(func); 731 732<span class="hljs-title function_">callsfunc</span>(); 733<span class="hljs-comment">// Tracker was called once</span> 734assert.<span class="hljs-title function_">strictEqual</span>(tracker.<span class="hljs-title function_">getCalls</span>(callsfunc).<span class="hljs-property">length</span>, <span class="hljs-number">1</span>); 735 736tracker.<span class="hljs-title function_">reset</span>(callsfunc); 737assert.<span class="hljs-title function_">strictEqual</span>(tracker.<span class="hljs-title function_">getCalls</span>(callsfunc).<span class="hljs-property">length</span>, <span class="hljs-number">0</span>);</code><code class="language-js cjs"><span class="hljs-keyword">const</span> assert = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:assert'</span>); 738 739<span class="hljs-keyword">const</span> tracker = <span class="hljs-keyword">new</span> assert.<span class="hljs-title class_">CallTracker</span>(); 740 741<span class="hljs-keyword">function</span> <span class="hljs-title function_">func</span>(<span class="hljs-params"></span>) {} 742<span class="hljs-keyword">const</span> callsfunc = tracker.<span class="hljs-title function_">calls</span>(func); 743 744<span class="hljs-title function_">callsfunc</span>(); 745<span class="hljs-comment">// Tracker was called once</span> 746assert.<span class="hljs-title function_">strictEqual</span>(tracker.<span class="hljs-title function_">getCalls</span>(callsfunc).<span class="hljs-property">length</span>, <span class="hljs-number">1</span>); 747 748tracker.<span class="hljs-title function_">reset</span>(callsfunc); 749assert.<span class="hljs-title function_">strictEqual</span>(tracker.<span class="hljs-title function_">getCalls</span>(callsfunc).<span class="hljs-property">length</span>, <span class="hljs-number">0</span>);</code><button class="copy-button">copy</button></pre> 750<h4><code>tracker.verify()</code><span><a class="mark" href="#trackerverify" id="trackerverify">#</a></span><a aria-hidden="true" class="legacy" id="assert_tracker_verify"></a></h4> 751<div class="api_metadata"> 752<span>Added in: v14.2.0, v12.19.0</span> 753</div> 754<p>Iterates through the list of functions passed to 755<a href="#trackercallsfn-exact"><code>tracker.calls()</code></a> and will throw an error for functions that 756have not been called the expected number of times.</p> 757 758<pre class="with-38-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> assert <span class="hljs-keyword">from</span> <span class="hljs-string">'node:assert'</span>; 759 760<span class="hljs-comment">// Creates call tracker.</span> 761<span class="hljs-keyword">const</span> tracker = <span class="hljs-keyword">new</span> assert.<span class="hljs-title class_">CallTracker</span>(); 762 763<span class="hljs-keyword">function</span> <span class="hljs-title function_">func</span>(<span class="hljs-params"></span>) {} 764 765<span class="hljs-comment">// Returns a function that wraps func() that must be called exact times</span> 766<span class="hljs-comment">// before tracker.verify().</span> 767<span class="hljs-keyword">const</span> callsfunc = tracker.<span class="hljs-title function_">calls</span>(func, <span class="hljs-number">2</span>); 768 769<span class="hljs-title function_">callsfunc</span>(); 770 771<span class="hljs-comment">// Will throw an error since callsfunc() was only called once.</span> 772tracker.<span class="hljs-title function_">verify</span>();</code><code class="language-js cjs"><span class="hljs-keyword">const</span> assert = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:assert'</span>); 773 774<span class="hljs-comment">// Creates call tracker.</span> 775<span class="hljs-keyword">const</span> tracker = <span class="hljs-keyword">new</span> assert.<span class="hljs-title class_">CallTracker</span>(); 776 777<span class="hljs-keyword">function</span> <span class="hljs-title function_">func</span>(<span class="hljs-params"></span>) {} 778 779<span class="hljs-comment">// Returns a function that wraps func() that must be called exact times</span> 780<span class="hljs-comment">// before tracker.verify().</span> 781<span class="hljs-keyword">const</span> callsfunc = tracker.<span class="hljs-title function_">calls</span>(func, <span class="hljs-number">2</span>); 782 783<span class="hljs-title function_">callsfunc</span>(); 784 785<span class="hljs-comment">// Will throw an error since callsfunc() was only called once.</span> 786tracker.<span class="hljs-title function_">verify</span>();</code><button class="copy-button">copy</button></pre> 787</section><section><h3><code>assert(value[, message])</code><span><a class="mark" href="#assertvalue-message" id="assertvalue-message">#</a></span><a aria-hidden="true" class="legacy" id="assert_assert_value_message"></a></h3> 788<div class="api_metadata"> 789<span>Added in: v0.5.9</span> 790</div> 791<ul> 792<li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a> The input that is checked for being truthy.</li> 793<li><code>message</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error" class="type"><Error></a></li> 794</ul> 795<p>An alias of <a href="#assertokvalue-message"><code>assert.ok()</code></a>.</p> 796</section><section><h3><code>assert.deepEqual(actual, expected[, message])</code><span><a class="mark" href="#assertdeepequalactual-expected-message" id="assertdeepequalactual-expected-message">#</a></span><a aria-hidden="true" class="legacy" id="assert_assert_deepequal_actual_expected_message"></a></h3> 797<div class="api_metadata"> 798<details class="changelog"><summary>History</summary> 799<table> 800<tbody><tr><th>Version</th><th>Changes</th></tr> 801<tr><td>v18.0.0</td> 802<td><p>Regular expressions lastIndex property is now compared as well.</p></td></tr> 803<tr><td>v16.0.0, v14.18.0</td> 804<td><p>In Legacy assertion mode, changed status from Deprecated to Legacy.</p></td></tr> 805<tr><td>v14.0.0</td> 806<td><p>NaN is now treated as being identical if both sides are NaN.</p></td></tr> 807<tr><td>v12.0.0</td> 808<td><p>The type tags are now properly compared and there are a couple minor comparison adjustments to make the check less surprising.</p></td></tr> 809<tr><td>v9.0.0</td> 810<td><p>The <code>Error</code> names and messages are now properly compared.</p></td></tr> 811<tr><td>v8.0.0</td> 812<td><p>The <code>Set</code> and <code>Map</code> content is also compared.</p></td></tr> 813<tr><td>v6.4.0, v4.7.1</td> 814<td><p>Typed array slices are handled correctly now.</p></td></tr> 815<tr><td>v6.1.0, v4.5.0</td> 816<td><p>Objects with circular references can be used as inputs now.</p></td></tr> 817<tr><td>v5.10.1, v4.4.3</td> 818<td><p>Handle non-<code>Uint8Array</code> typed arrays correctly.</p></td></tr> 819<tr><td>v0.1.21</td> 820<td><p><span>Added in: v0.1.21</span></p></td></tr> 821</tbody></table> 822</details> 823</div> 824<ul> 825<li><code>actual</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 826<li><code>expected</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 827<li><code>message</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error" class="type"><Error></a></li> 828</ul> 829<p><strong>Strict assertion mode</strong></p> 830<p>An alias of <a href="#assertdeepstrictequalactual-expected-message"><code>assert.deepStrictEqual()</code></a>.</p> 831<p><strong>Legacy assertion mode</strong></p> 832<p></p><div class="api_stability api_stability_3"><a href="documentation.html#stability-index">Stability: 3</a> - Legacy: Use <a href="#assertdeepstrictequalactual-expected-message"><code>assert.deepStrictEqual()</code></a> instead.</div><p></p> 833<p>Tests for deep equality between the <code>actual</code> and <code>expected</code> parameters. Consider 834using <a href="#assertdeepstrictequalactual-expected-message"><code>assert.deepStrictEqual()</code></a> instead. <a href="#assertdeepequalactual-expected-message"><code>assert.deepEqual()</code></a> can have 835surprising results.</p> 836<p><em>Deep equality</em> means that the enumerable "own" properties of child objects 837are also recursively evaluated by the following rules.</p> 838<h4>Comparison details<span><a class="mark" href="#comparison-details" id="comparison-details">#</a></span><a aria-hidden="true" class="legacy" id="assert_comparison_details"></a></h4> 839<ul> 840<li>Primitive values are compared with the <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Equality"><code>==</code> operator</a>, 841with the exception of <code>NaN</code>. It is treated as being identical in case 842both sides are <code>NaN</code>.</li> 843<li><a href="https://tc39.github.io/ecma262/#sec-object.prototype.tostring">Type tags</a> of objects should be the same.</li> 844<li>Only <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Enumerability_and_ownership_of_properties">enumerable "own" properties</a> are considered.</li> 845<li><a href="errors.html#class-error"><code>Error</code></a> names and messages are always compared, even if these are not 846enumerable properties.</li> 847<li><a href="https://developer.mozilla.org/en-US/docs/Glossary/Primitive#Primitive_wrapper_objects_in_JavaScript">Object wrappers</a> are compared both as objects and unwrapped values.</li> 848<li><code>Object</code> properties are compared unordered.</li> 849<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Map"><code>Map</code></a> keys and <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Set"><code>Set</code></a> items are compared unordered.</li> 850<li>Recursion stops when both sides differ or both sides encounter a circular 851reference.</li> 852<li>Implementation does not test the <a href="https://tc39.github.io/ecma262/#sec-ordinary-object-internal-methods-and-internal-slots"><code>[[Prototype]]</code></a> of 853objects.</li> 854<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Symbol"><code>Symbol</code></a> properties are not compared.</li> 855<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/WeakMap"><code>WeakMap</code></a> and <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/WeakSet"><code>WeakSet</code></a> comparison does not rely on their values.</li> 856<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Regular_Expressions"><code>RegExp</code></a> lastIndex, flags, and source are always compared, even if these 857are not enumerable properties.</li> 858</ul> 859<p>The following example does not throw an <a href="#class-assertassertionerror"><code>AssertionError</code></a> because the 860primitives are compared using the <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Equality"><code>==</code> operator</a>.</p> 861 862<pre class="with-50-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> assert <span class="hljs-keyword">from</span> <span class="hljs-string">'node:assert'</span>; 863<span class="hljs-comment">// WARNING: This does not throw an AssertionError!</span> 864 865assert.<span class="hljs-title function_">deepEqual</span>(<span class="hljs-string">'+00000000'</span>, <span class="hljs-literal">false</span>);</code><code class="language-js cjs"><span class="hljs-keyword">const</span> assert = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:assert'</span>); 866<span class="hljs-comment">// WARNING: This does not throw an AssertionError!</span> 867 868assert.<span class="hljs-title function_">deepEqual</span>(<span class="hljs-string">'+00000000'</span>, <span class="hljs-literal">false</span>);</code><button class="copy-button">copy</button></pre> 869<p>"Deep" equality means that the enumerable "own" properties of child objects 870are evaluated also:</p> 871 872<pre class="with-38-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> assert <span class="hljs-keyword">from</span> <span class="hljs-string">'node:assert'</span>; 873 874<span class="hljs-keyword">const</span> obj1 = { 875 <span class="hljs-attr">a</span>: { 876 <span class="hljs-attr">b</span>: <span class="hljs-number">1</span>, 877 }, 878}; 879<span class="hljs-keyword">const</span> obj2 = { 880 <span class="hljs-attr">a</span>: { 881 <span class="hljs-attr">b</span>: <span class="hljs-number">2</span>, 882 }, 883}; 884<span class="hljs-keyword">const</span> obj3 = { 885 <span class="hljs-attr">a</span>: { 886 <span class="hljs-attr">b</span>: <span class="hljs-number">1</span>, 887 }, 888}; 889<span class="hljs-keyword">const</span> obj4 = <span class="hljs-title class_">Object</span>.<span class="hljs-title function_">create</span>(obj1); 890 891assert.<span class="hljs-title function_">deepEqual</span>(obj1, obj1); 892<span class="hljs-comment">// OK</span> 893 894<span class="hljs-comment">// Values of b are different:</span> 895assert.<span class="hljs-title function_">deepEqual</span>(obj1, obj2); 896<span class="hljs-comment">// AssertionError: { a: { b: 1 } } deepEqual { a: { b: 2 } }</span> 897 898assert.<span class="hljs-title function_">deepEqual</span>(obj1, obj3); 899<span class="hljs-comment">// OK</span> 900 901<span class="hljs-comment">// Prototypes are ignored:</span> 902assert.<span class="hljs-title function_">deepEqual</span>(obj1, obj4); 903<span class="hljs-comment">// AssertionError: { a: { b: 1 } } deepEqual {}</span></code><code class="language-js cjs"><span class="hljs-keyword">const</span> assert = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:assert'</span>); 904 905<span class="hljs-keyword">const</span> obj1 = { 906 <span class="hljs-attr">a</span>: { 907 <span class="hljs-attr">b</span>: <span class="hljs-number">1</span>, 908 }, 909}; 910<span class="hljs-keyword">const</span> obj2 = { 911 <span class="hljs-attr">a</span>: { 912 <span class="hljs-attr">b</span>: <span class="hljs-number">2</span>, 913 }, 914}; 915<span class="hljs-keyword">const</span> obj3 = { 916 <span class="hljs-attr">a</span>: { 917 <span class="hljs-attr">b</span>: <span class="hljs-number">1</span>, 918 }, 919}; 920<span class="hljs-keyword">const</span> obj4 = <span class="hljs-title class_">Object</span>.<span class="hljs-title function_">create</span>(obj1); 921 922assert.<span class="hljs-title function_">deepEqual</span>(obj1, obj1); 923<span class="hljs-comment">// OK</span> 924 925<span class="hljs-comment">// Values of b are different:</span> 926assert.<span class="hljs-title function_">deepEqual</span>(obj1, obj2); 927<span class="hljs-comment">// AssertionError: { a: { b: 1 } } deepEqual { a: { b: 2 } }</span> 928 929assert.<span class="hljs-title function_">deepEqual</span>(obj1, obj3); 930<span class="hljs-comment">// OK</span> 931 932<span class="hljs-comment">// Prototypes are ignored:</span> 933assert.<span class="hljs-title function_">deepEqual</span>(obj1, obj4); 934<span class="hljs-comment">// AssertionError: { a: { b: 1 } } deepEqual {}</span></code><button class="copy-button">copy</button></pre> 935<p>If the values are not equal, an <a href="#class-assertassertionerror"><code>AssertionError</code></a> is thrown with a <code>message</code> 936property set equal to the value of the <code>message</code> parameter. If the <code>message</code> 937parameter is undefined, a default error message is assigned. If the <code>message</code> 938parameter is an instance of an <a href="errors.html#class-error"><code>Error</code></a> then it will be thrown instead of the 939<a href="#class-assertassertionerror"><code>AssertionError</code></a>.</p> 940</section><section><h3><code>assert.deepStrictEqual(actual, expected[, message])</code><span><a class="mark" href="#assertdeepstrictequalactual-expected-message" id="assertdeepstrictequalactual-expected-message">#</a></span><a aria-hidden="true" class="legacy" id="assert_assert_deepstrictequal_actual_expected_message"></a></h3> 941<div class="api_metadata"> 942<details class="changelog"><summary>History</summary> 943<table> 944<tbody><tr><th>Version</th><th>Changes</th></tr> 945<tr><td>v18.0.0</td> 946<td><p>Regular expressions lastIndex property is now compared as well.</p></td></tr> 947<tr><td>v9.0.0</td> 948<td><p>Enumerable symbol properties are now compared.</p></td></tr> 949<tr><td>v9.0.0</td> 950<td><p>The <code>NaN</code> is now compared using the <a href="https://tc39.github.io/ecma262/#sec-samevaluezero">SameValueZero</a> comparison.</p></td></tr> 951<tr><td>v8.5.0</td> 952<td><p>The <code>Error</code> names and messages are now properly compared.</p></td></tr> 953<tr><td>v8.0.0</td> 954<td><p>The <code>Set</code> and <code>Map</code> content is also compared.</p></td></tr> 955<tr><td>v6.1.0</td> 956<td><p>Objects with circular references can be used as inputs now.</p></td></tr> 957<tr><td>v6.4.0, v4.7.1</td> 958<td><p>Typed array slices are handled correctly now.</p></td></tr> 959<tr><td>v5.10.1, v4.4.3</td> 960<td><p>Handle non-<code>Uint8Array</code> typed arrays correctly.</p></td></tr> 961<tr><td>v1.2.0</td> 962<td><p><span>Added in: v1.2.0</span></p></td></tr> 963</tbody></table> 964</details> 965</div> 966<ul> 967<li><code>actual</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 968<li><code>expected</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 969<li><code>message</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error" class="type"><Error></a></li> 970</ul> 971<p>Tests for deep equality between the <code>actual</code> and <code>expected</code> parameters. 972"Deep" equality means that the enumerable "own" properties of child objects 973are recursively evaluated also by the following rules.</p> 974<h4>Comparison details<span><a class="mark" href="#comparison-details_1" id="comparison-details_1">#</a></span><a aria-hidden="true" class="legacy" id="assert_comparison_details_1"></a></h4> 975<ul> 976<li>Primitive values are compared using <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/is"><code>Object.is()</code></a>.</li> 977<li><a href="https://tc39.github.io/ecma262/#sec-object.prototype.tostring">Type tags</a> of objects should be the same.</li> 978<li><a href="https://tc39.github.io/ecma262/#sec-ordinary-object-internal-methods-and-internal-slots"><code>[[Prototype]]</code></a> of objects are compared using 979the <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Strict_equality"><code>===</code> operator</a>.</li> 980<li>Only <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Enumerability_and_ownership_of_properties">enumerable "own" properties</a> are considered.</li> 981<li><a href="errors.html#class-error"><code>Error</code></a> names and messages are always compared, even if these are not 982enumerable properties.</li> 983<li>Enumerable own <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Symbol"><code>Symbol</code></a> properties are compared as well.</li> 984<li><a href="https://developer.mozilla.org/en-US/docs/Glossary/Primitive#Primitive_wrapper_objects_in_JavaScript">Object wrappers</a> are compared both as objects and unwrapped values.</li> 985<li><code>Object</code> properties are compared unordered.</li> 986<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Map"><code>Map</code></a> keys and <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Set"><code>Set</code></a> items are compared unordered.</li> 987<li>Recursion stops when both sides differ or both sides encounter a circular 988reference.</li> 989<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/WeakMap"><code>WeakMap</code></a> and <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/WeakSet"><code>WeakSet</code></a> comparison does not rely on their values. See 990below for further details.</li> 991<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Regular_Expressions"><code>RegExp</code></a> lastIndex, flags, and source are always compared, even if these 992are not enumerable properties.</li> 993</ul> 994 995<pre class="with-45-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> assert <span class="hljs-keyword">from</span> <span class="hljs-string">'node:assert/strict'</span>; 996 997<span class="hljs-comment">// This fails because 1 !== '1'.</span> 998assert.<span class="hljs-title function_">deepStrictEqual</span>({ <span class="hljs-attr">a</span>: <span class="hljs-number">1</span> }, { <span class="hljs-attr">a</span>: <span class="hljs-string">'1'</span> }); 999<span class="hljs-comment">// AssertionError: Expected inputs to be strictly deep-equal:</span> 1000<span class="hljs-comment">// + actual - expected</span> 1001<span class="hljs-comment">//</span> 1002<span class="hljs-comment">// {</span> 1003<span class="hljs-comment">// + a: 1</span> 1004<span class="hljs-comment">// - a: '1'</span> 1005<span class="hljs-comment">// }</span> 1006 1007<span class="hljs-comment">// The following objects don't have own properties</span> 1008<span class="hljs-keyword">const</span> date = <span class="hljs-keyword">new</span> <span class="hljs-title class_">Date</span>(); 1009<span class="hljs-keyword">const</span> object = {}; 1010<span class="hljs-keyword">const</span> fakeDate = {}; 1011<span class="hljs-title class_">Object</span>.<span class="hljs-title function_">setPrototypeOf</span>(fakeDate, <span class="hljs-title class_">Date</span>.<span class="hljs-property"><span class="hljs-keyword">prototype</span></span>); 1012 1013<span class="hljs-comment">// Different [[Prototype]]:</span> 1014assert.<span class="hljs-title function_">deepStrictEqual</span>(object, fakeDate); 1015<span class="hljs-comment">// AssertionError: Expected inputs to be strictly deep-equal:</span> 1016<span class="hljs-comment">// + actual - expected</span> 1017<span class="hljs-comment">//</span> 1018<span class="hljs-comment">// + {}</span> 1019<span class="hljs-comment">// - Date {}</span> 1020 1021<span class="hljs-comment">// Different type tags:</span> 1022assert.<span class="hljs-title function_">deepStrictEqual</span>(date, fakeDate); 1023<span class="hljs-comment">// AssertionError: Expected inputs to be strictly deep-equal:</span> 1024<span class="hljs-comment">// + actual - expected</span> 1025<span class="hljs-comment">//</span> 1026<span class="hljs-comment">// + 2018-04-26T00:49:08.604Z</span> 1027<span class="hljs-comment">// - Date {}</span> 1028 1029assert.<span class="hljs-title function_">deepStrictEqual</span>(<span class="hljs-title class_">NaN</span>, <span class="hljs-title class_">NaN</span>); 1030<span class="hljs-comment">// OK because Object.is(NaN, NaN) is true.</span> 1031 1032<span class="hljs-comment">// Different unwrapped numbers:</span> 1033assert.<span class="hljs-title function_">deepStrictEqual</span>(<span class="hljs-keyword">new</span> <span class="hljs-title class_">Number</span>(<span class="hljs-number">1</span>), <span class="hljs-keyword">new</span> <span class="hljs-title class_">Number</span>(<span class="hljs-number">2</span>)); 1034<span class="hljs-comment">// AssertionError: Expected inputs to be strictly deep-equal:</span> 1035<span class="hljs-comment">// + actual - expected</span> 1036<span class="hljs-comment">//</span> 1037<span class="hljs-comment">// + [Number: 1]</span> 1038<span class="hljs-comment">// - [Number: 2]</span> 1039 1040assert.<span class="hljs-title function_">deepStrictEqual</span>(<span class="hljs-keyword">new</span> <span class="hljs-title class_">String</span>(<span class="hljs-string">'foo'</span>), <span class="hljs-title class_">Object</span>(<span class="hljs-string">'foo'</span>)); 1041<span class="hljs-comment">// OK because the object and the string are identical when unwrapped.</span> 1042 1043assert.<span class="hljs-title function_">deepStrictEqual</span>(-<span class="hljs-number">0</span>, -<span class="hljs-number">0</span>); 1044<span class="hljs-comment">// OK</span> 1045 1046<span class="hljs-comment">// Different zeros:</span> 1047assert.<span class="hljs-title function_">deepStrictEqual</span>(<span class="hljs-number">0</span>, -<span class="hljs-number">0</span>); 1048<span class="hljs-comment">// AssertionError: Expected inputs to be strictly deep-equal:</span> 1049<span class="hljs-comment">// + actual - expected</span> 1050<span class="hljs-comment">//</span> 1051<span class="hljs-comment">// + 0</span> 1052<span class="hljs-comment">// - -0</span> 1053 1054<span class="hljs-keyword">const</span> symbol1 = <span class="hljs-title class_">Symbol</span>(); 1055<span class="hljs-keyword">const</span> symbol2 = <span class="hljs-title class_">Symbol</span>(); 1056assert.<span class="hljs-title function_">deepStrictEqual</span>({ [symbol1]: <span class="hljs-number">1</span> }, { [symbol1]: <span class="hljs-number">1</span> }); 1057<span class="hljs-comment">// OK, because it is the same symbol on both objects.</span> 1058 1059assert.<span class="hljs-title function_">deepStrictEqual</span>({ [symbol1]: <span class="hljs-number">1</span> }, { [symbol2]: <span class="hljs-number">1</span> }); 1060<span class="hljs-comment">// AssertionError [ERR_ASSERTION]: Inputs identical but not reference equal:</span> 1061<span class="hljs-comment">//</span> 1062<span class="hljs-comment">// {</span> 1063<span class="hljs-comment">// [Symbol()]: 1</span> 1064<span class="hljs-comment">// }</span> 1065 1066<span class="hljs-keyword">const</span> weakMap1 = <span class="hljs-keyword">new</span> <span class="hljs-title class_">WeakMap</span>(); 1067<span class="hljs-keyword">const</span> weakMap2 = <span class="hljs-keyword">new</span> <span class="hljs-title class_">WeakMap</span>([[{}, {}]]); 1068<span class="hljs-keyword">const</span> weakMap3 = <span class="hljs-keyword">new</span> <span class="hljs-title class_">WeakMap</span>(); 1069weakMap3.<span class="hljs-property">unequal</span> = <span class="hljs-literal">true</span>; 1070 1071assert.<span class="hljs-title function_">deepStrictEqual</span>(weakMap1, weakMap2); 1072<span class="hljs-comment">// OK, because it is impossible to compare the entries</span> 1073 1074<span class="hljs-comment">// Fails because weakMap3 has a property that weakMap1 does not contain:</span> 1075assert.<span class="hljs-title function_">deepStrictEqual</span>(weakMap1, weakMap3); 1076<span class="hljs-comment">// AssertionError: Expected inputs to be strictly deep-equal:</span> 1077<span class="hljs-comment">// + actual - expected</span> 1078<span class="hljs-comment">//</span> 1079<span class="hljs-comment">// WeakMap {</span> 1080<span class="hljs-comment">// + [items unknown]</span> 1081<span class="hljs-comment">// - [items unknown],</span> 1082<span class="hljs-comment">// - unequal: true</span> 1083<span class="hljs-comment">// }</span></code><code class="language-js cjs"><span class="hljs-keyword">const</span> assert = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:assert/strict'</span>); 1084 1085<span class="hljs-comment">// This fails because 1 !== '1'.</span> 1086assert.<span class="hljs-title function_">deepStrictEqual</span>({ <span class="hljs-attr">a</span>: <span class="hljs-number">1</span> }, { <span class="hljs-attr">a</span>: <span class="hljs-string">'1'</span> }); 1087<span class="hljs-comment">// AssertionError: Expected inputs to be strictly deep-equal:</span> 1088<span class="hljs-comment">// + actual - expected</span> 1089<span class="hljs-comment">//</span> 1090<span class="hljs-comment">// {</span> 1091<span class="hljs-comment">// + a: 1</span> 1092<span class="hljs-comment">// - a: '1'</span> 1093<span class="hljs-comment">// }</span> 1094 1095<span class="hljs-comment">// The following objects don't have own properties</span> 1096<span class="hljs-keyword">const</span> date = <span class="hljs-keyword">new</span> <span class="hljs-title class_">Date</span>(); 1097<span class="hljs-keyword">const</span> object = {}; 1098<span class="hljs-keyword">const</span> fakeDate = {}; 1099<span class="hljs-title class_">Object</span>.<span class="hljs-title function_">setPrototypeOf</span>(fakeDate, <span class="hljs-title class_">Date</span>.<span class="hljs-property"><span class="hljs-keyword">prototype</span></span>); 1100 1101<span class="hljs-comment">// Different [[Prototype]]:</span> 1102assert.<span class="hljs-title function_">deepStrictEqual</span>(object, fakeDate); 1103<span class="hljs-comment">// AssertionError: Expected inputs to be strictly deep-equal:</span> 1104<span class="hljs-comment">// + actual - expected</span> 1105<span class="hljs-comment">//</span> 1106<span class="hljs-comment">// + {}</span> 1107<span class="hljs-comment">// - Date {}</span> 1108 1109<span class="hljs-comment">// Different type tags:</span> 1110assert.<span class="hljs-title function_">deepStrictEqual</span>(date, fakeDate); 1111<span class="hljs-comment">// AssertionError: Expected inputs to be strictly deep-equal:</span> 1112<span class="hljs-comment">// + actual - expected</span> 1113<span class="hljs-comment">//</span> 1114<span class="hljs-comment">// + 2018-04-26T00:49:08.604Z</span> 1115<span class="hljs-comment">// - Date {}</span> 1116 1117assert.<span class="hljs-title function_">deepStrictEqual</span>(<span class="hljs-title class_">NaN</span>, <span class="hljs-title class_">NaN</span>); 1118<span class="hljs-comment">// OK because Object.is(NaN, NaN) is true.</span> 1119 1120<span class="hljs-comment">// Different unwrapped numbers:</span> 1121assert.<span class="hljs-title function_">deepStrictEqual</span>(<span class="hljs-keyword">new</span> <span class="hljs-title class_">Number</span>(<span class="hljs-number">1</span>), <span class="hljs-keyword">new</span> <span class="hljs-title class_">Number</span>(<span class="hljs-number">2</span>)); 1122<span class="hljs-comment">// AssertionError: Expected inputs to be strictly deep-equal:</span> 1123<span class="hljs-comment">// + actual - expected</span> 1124<span class="hljs-comment">//</span> 1125<span class="hljs-comment">// + [Number: 1]</span> 1126<span class="hljs-comment">// - [Number: 2]</span> 1127 1128assert.<span class="hljs-title function_">deepStrictEqual</span>(<span class="hljs-keyword">new</span> <span class="hljs-title class_">String</span>(<span class="hljs-string">'foo'</span>), <span class="hljs-title class_">Object</span>(<span class="hljs-string">'foo'</span>)); 1129<span class="hljs-comment">// OK because the object and the string are identical when unwrapped.</span> 1130 1131assert.<span class="hljs-title function_">deepStrictEqual</span>(-<span class="hljs-number">0</span>, -<span class="hljs-number">0</span>); 1132<span class="hljs-comment">// OK</span> 1133 1134<span class="hljs-comment">// Different zeros:</span> 1135assert.<span class="hljs-title function_">deepStrictEqual</span>(<span class="hljs-number">0</span>, -<span class="hljs-number">0</span>); 1136<span class="hljs-comment">// AssertionError: Expected inputs to be strictly deep-equal:</span> 1137<span class="hljs-comment">// + actual - expected</span> 1138<span class="hljs-comment">//</span> 1139<span class="hljs-comment">// + 0</span> 1140<span class="hljs-comment">// - -0</span> 1141 1142<span class="hljs-keyword">const</span> symbol1 = <span class="hljs-title class_">Symbol</span>(); 1143<span class="hljs-keyword">const</span> symbol2 = <span class="hljs-title class_">Symbol</span>(); 1144assert.<span class="hljs-title function_">deepStrictEqual</span>({ [symbol1]: <span class="hljs-number">1</span> }, { [symbol1]: <span class="hljs-number">1</span> }); 1145<span class="hljs-comment">// OK, because it is the same symbol on both objects.</span> 1146 1147assert.<span class="hljs-title function_">deepStrictEqual</span>({ [symbol1]: <span class="hljs-number">1</span> }, { [symbol2]: <span class="hljs-number">1</span> }); 1148<span class="hljs-comment">// AssertionError [ERR_ASSERTION]: Inputs identical but not reference equal:</span> 1149<span class="hljs-comment">//</span> 1150<span class="hljs-comment">// {</span> 1151<span class="hljs-comment">// [Symbol()]: 1</span> 1152<span class="hljs-comment">// }</span> 1153 1154<span class="hljs-keyword">const</span> weakMap1 = <span class="hljs-keyword">new</span> <span class="hljs-title class_">WeakMap</span>(); 1155<span class="hljs-keyword">const</span> weakMap2 = <span class="hljs-keyword">new</span> <span class="hljs-title class_">WeakMap</span>([[{}, {}]]); 1156<span class="hljs-keyword">const</span> weakMap3 = <span class="hljs-keyword">new</span> <span class="hljs-title class_">WeakMap</span>(); 1157weakMap3.<span class="hljs-property">unequal</span> = <span class="hljs-literal">true</span>; 1158 1159assert.<span class="hljs-title function_">deepStrictEqual</span>(weakMap1, weakMap2); 1160<span class="hljs-comment">// OK, because it is impossible to compare the entries</span> 1161 1162<span class="hljs-comment">// Fails because weakMap3 has a property that weakMap1 does not contain:</span> 1163assert.<span class="hljs-title function_">deepStrictEqual</span>(weakMap1, weakMap3); 1164<span class="hljs-comment">// AssertionError: Expected inputs to be strictly deep-equal:</span> 1165<span class="hljs-comment">// + actual - expected</span> 1166<span class="hljs-comment">//</span> 1167<span class="hljs-comment">// WeakMap {</span> 1168<span class="hljs-comment">// + [items unknown]</span> 1169<span class="hljs-comment">// - [items unknown],</span> 1170<span class="hljs-comment">// - unequal: true</span> 1171<span class="hljs-comment">// }</span></code><button class="copy-button">copy</button></pre> 1172<p>If the values are not equal, an <a href="#class-assertassertionerror"><code>AssertionError</code></a> is thrown with a <code>message</code> 1173property set equal to the value of the <code>message</code> parameter. If the <code>message</code> 1174parameter is undefined, a default error message is assigned. If the <code>message</code> 1175parameter is an instance of an <a href="errors.html#class-error"><code>Error</code></a> then it will be thrown instead of the 1176<code>AssertionError</code>.</p> 1177</section><section><h3><code>assert.doesNotMatch(string, regexp[, message])</code><span><a class="mark" href="#assertdoesnotmatchstring-regexp-message" id="assertdoesnotmatchstring-regexp-message">#</a></span><a aria-hidden="true" class="legacy" id="assert_assert_doesnotmatch_string_regexp_message"></a></h3> 1178<div class="api_metadata"> 1179<details class="changelog"><summary>History</summary> 1180<table> 1181<tbody><tr><th>Version</th><th>Changes</th></tr> 1182<tr><td>v16.0.0</td> 1183<td><p>This API is no longer experimental.</p></td></tr> 1184<tr><td>v13.6.0, v12.16.0</td> 1185<td><p><span>Added in: v13.6.0, v12.16.0</span></p></td></tr> 1186</tbody></table> 1187</details> 1188</div> 1189<ul> 1190<li><code>string</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 1191<li><code>regexp</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/RegExp" class="type"><RegExp></a></li> 1192<li><code>message</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error" class="type"><Error></a></li> 1193</ul> 1194<p>Expects the <code>string</code> input not to match the regular expression.</p> 1195 1196<pre class="with-45-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> assert <span class="hljs-keyword">from</span> <span class="hljs-string">'node:assert/strict'</span>; 1197 1198assert.<span class="hljs-title function_">doesNotMatch</span>(<span class="hljs-string">'I will fail'</span>, <span class="hljs-regexp">/fail/</span>); 1199<span class="hljs-comment">// AssertionError [ERR_ASSERTION]: The input was expected to not match the ...</span> 1200 1201assert.<span class="hljs-title function_">doesNotMatch</span>(<span class="hljs-number">123</span>, <span class="hljs-regexp">/pass/</span>); 1202<span class="hljs-comment">// AssertionError [ERR_ASSERTION]: The "string" argument must be of type string.</span> 1203 1204assert.<span class="hljs-title function_">doesNotMatch</span>(<span class="hljs-string">'I will pass'</span>, <span class="hljs-regexp">/different/</span>); 1205<span class="hljs-comment">// OK</span></code><code class="language-js cjs"><span class="hljs-keyword">const</span> assert = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:assert/strict'</span>); 1206 1207assert.<span class="hljs-title function_">doesNotMatch</span>(<span class="hljs-string">'I will fail'</span>, <span class="hljs-regexp">/fail/</span>); 1208<span class="hljs-comment">// AssertionError [ERR_ASSERTION]: The input was expected to not match the ...</span> 1209 1210assert.<span class="hljs-title function_">doesNotMatch</span>(<span class="hljs-number">123</span>, <span class="hljs-regexp">/pass/</span>); 1211<span class="hljs-comment">// AssertionError [ERR_ASSERTION]: The "string" argument must be of type string.</span> 1212 1213assert.<span class="hljs-title function_">doesNotMatch</span>(<span class="hljs-string">'I will pass'</span>, <span class="hljs-regexp">/different/</span>); 1214<span class="hljs-comment">// OK</span></code><button class="copy-button">copy</button></pre> 1215<p>If the values do match, or if the <code>string</code> argument is of another type than 1216<code>string</code>, an <a href="#class-assertassertionerror"><code>AssertionError</code></a> is thrown with a <code>message</code> property set equal 1217to the value of the <code>message</code> parameter. If the <code>message</code> parameter is 1218undefined, a default error message is assigned. If the <code>message</code> parameter is an 1219instance of an <a href="errors.html#class-error"><code>Error</code></a> then it will be thrown instead of the 1220<a href="#class-assertassertionerror"><code>AssertionError</code></a>.</p> 1221</section><section><h3><code>assert.doesNotReject(asyncFn[, error][, message])</code><span><a class="mark" href="#assertdoesnotrejectasyncfn-error-message" id="assertdoesnotrejectasyncfn-error-message">#</a></span><a aria-hidden="true" class="legacy" id="assert_assert_doesnotreject_asyncfn_error_message"></a></h3> 1222<div class="api_metadata"> 1223<span>Added in: v10.0.0</span> 1224</div> 1225<ul> 1226<li><code>asyncFn</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise" class="type"><Promise></a></li> 1227<li><code>error</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/RegExp" class="type"><RegExp></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a></li> 1228<li><code>message</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 1229</ul> 1230<p>Awaits the <code>asyncFn</code> promise or, if <code>asyncFn</code> is a function, immediately 1231calls the function and awaits the returned promise to complete. It will then 1232check that the promise is not rejected.</p> 1233<p>If <code>asyncFn</code> is a function and it throws an error synchronously, 1234<code>assert.doesNotReject()</code> will return a rejected <code>Promise</code> with that error. If 1235the function does not return a promise, <code>assert.doesNotReject()</code> will return a 1236rejected <code>Promise</code> with an <a href="errors.html#err_invalid_return_value"><code>ERR_INVALID_RETURN_VALUE</code></a> error. In both cases 1237the error handler is skipped.</p> 1238<p>Using <code>assert.doesNotReject()</code> is actually not useful because there is little 1239benefit in catching a rejection and then rejecting it again. Instead, consider 1240adding a comment next to the specific code path that should not reject and keep 1241error messages as expressive as possible.</p> 1242<p>If specified, <code>error</code> can be a <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Classes"><code>Class</code></a>, <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Regular_Expressions"><code>RegExp</code></a>, or a validation 1243function. See <a href="#assertthrowsfn-error-message"><code>assert.throws()</code></a> for more details.</p> 1244<p>Besides the async nature to await the completion behaves identically to 1245<a href="#assertdoesnotthrowfn-error-message"><code>assert.doesNotThrow()</code></a>.</p> 1246 1247<pre class="with-45-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> assert <span class="hljs-keyword">from</span> <span class="hljs-string">'node:assert/strict'</span>; 1248 1249<span class="hljs-keyword">await</span> assert.<span class="hljs-title function_">doesNotReject</span>( 1250 <span class="hljs-keyword">async</span> () => { 1251 <span class="hljs-keyword">throw</span> <span class="hljs-keyword">new</span> <span class="hljs-title class_">TypeError</span>(<span class="hljs-string">'Wrong value'</span>); 1252 }, 1253 <span class="hljs-title class_">SyntaxError</span>, 1254);</code><code class="language-js cjs"><span class="hljs-keyword">const</span> assert = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:assert/strict'</span>); 1255 1256(<span class="hljs-keyword">async</span> () => { 1257 <span class="hljs-keyword">await</span> assert.<span class="hljs-title function_">doesNotReject</span>( 1258 <span class="hljs-keyword">async</span> () => { 1259 <span class="hljs-keyword">throw</span> <span class="hljs-keyword">new</span> <span class="hljs-title class_">TypeError</span>(<span class="hljs-string">'Wrong value'</span>); 1260 }, 1261 <span class="hljs-title class_">SyntaxError</span>, 1262 ); 1263})();</code><button class="copy-button">copy</button></pre> 1264 1265<pre class="with-45-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> assert <span class="hljs-keyword">from</span> <span class="hljs-string">'node:assert/strict'</span>; 1266 1267assert.<span class="hljs-title function_">doesNotReject</span>(<span class="hljs-title class_">Promise</span>.<span class="hljs-title function_">reject</span>(<span class="hljs-keyword">new</span> <span class="hljs-title class_">TypeError</span>(<span class="hljs-string">'Wrong value'</span>))) 1268 .<span class="hljs-title function_">then</span>(<span class="hljs-function">() =></span> { 1269 <span class="hljs-comment">// ...</span> 1270 });</code><code class="language-js cjs"><span class="hljs-keyword">const</span> assert = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:assert/strict'</span>); 1271 1272assert.<span class="hljs-title function_">doesNotReject</span>(<span class="hljs-title class_">Promise</span>.<span class="hljs-title function_">reject</span>(<span class="hljs-keyword">new</span> <span class="hljs-title class_">TypeError</span>(<span class="hljs-string">'Wrong value'</span>))) 1273 .<span class="hljs-title function_">then</span>(<span class="hljs-function">() =></span> { 1274 <span class="hljs-comment">// ...</span> 1275 });</code><button class="copy-button">copy</button></pre> 1276</section><section><h3><code>assert.doesNotThrow(fn[, error][, message])</code><span><a class="mark" href="#assertdoesnotthrowfn-error-message" id="assertdoesnotthrowfn-error-message">#</a></span><a aria-hidden="true" class="legacy" id="assert_assert_doesnotthrow_fn_error_message"></a></h3> 1277<div class="api_metadata"> 1278<details class="changelog"><summary>History</summary> 1279<table> 1280<tbody><tr><th>Version</th><th>Changes</th></tr> 1281<tr><td>v5.11.0, v4.4.5</td> 1282<td><p>The <code>message</code> parameter is respected now.</p></td></tr> 1283<tr><td>v4.2.0</td> 1284<td><p>The <code>error</code> parameter can now be an arrow function.</p></td></tr> 1285<tr><td>v0.1.21</td> 1286<td><p><span>Added in: v0.1.21</span></p></td></tr> 1287</tbody></table> 1288</details> 1289</div> 1290<ul> 1291<li><code>fn</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a></li> 1292<li><code>error</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/RegExp" class="type"><RegExp></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a></li> 1293<li><code>message</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 1294</ul> 1295<p>Asserts that the function <code>fn</code> does not throw an error.</p> 1296<p>Using <code>assert.doesNotThrow()</code> is actually not useful because there 1297is no benefit in catching an error and then rethrowing it. Instead, consider 1298adding a comment next to the specific code path that should not throw and keep 1299error messages as expressive as possible.</p> 1300<p>When <code>assert.doesNotThrow()</code> is called, it will immediately call the <code>fn</code> 1301function.</p> 1302<p>If an error is thrown and it is the same type as that specified by the <code>error</code> 1303parameter, then an <a href="#class-assertassertionerror"><code>AssertionError</code></a> is thrown. If the error is of a 1304different type, or if the <code>error</code> parameter is undefined, the error is 1305propagated back to the caller.</p> 1306<p>If specified, <code>error</code> can be a <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Classes"><code>Class</code></a>, <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Regular_Expressions"><code>RegExp</code></a>, or a validation 1307function. See <a href="#assertthrowsfn-error-message"><code>assert.throws()</code></a> for more details.</p> 1308<p>The following, for instance, will throw the <a href="errors.html#class-typeerror"><code>TypeError</code></a> because there is no 1309matching error type in the assertion:</p> 1310 1311<pre class="with-45-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> assert <span class="hljs-keyword">from</span> <span class="hljs-string">'node:assert/strict'</span>; 1312 1313assert.<span class="hljs-title function_">doesNotThrow</span>( 1314 <span class="hljs-function">() =></span> { 1315 <span class="hljs-keyword">throw</span> <span class="hljs-keyword">new</span> <span class="hljs-title class_">TypeError</span>(<span class="hljs-string">'Wrong value'</span>); 1316 }, 1317 <span class="hljs-title class_">SyntaxError</span>, 1318);</code><code class="language-js cjs"><span class="hljs-keyword">const</span> assert = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:assert/strict'</span>); 1319 1320assert.<span class="hljs-title function_">doesNotThrow</span>( 1321 <span class="hljs-function">() =></span> { 1322 <span class="hljs-keyword">throw</span> <span class="hljs-keyword">new</span> <span class="hljs-title class_">TypeError</span>(<span class="hljs-string">'Wrong value'</span>); 1323 }, 1324 <span class="hljs-title class_">SyntaxError</span>, 1325);</code><button class="copy-button">copy</button></pre> 1326<p>However, the following will result in an <a href="#class-assertassertionerror"><code>AssertionError</code></a> with the message 1327'Got unwanted exception...':</p> 1328 1329<pre class="with-45-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> assert <span class="hljs-keyword">from</span> <span class="hljs-string">'node:assert/strict'</span>; 1330 1331assert.<span class="hljs-title function_">doesNotThrow</span>( 1332 <span class="hljs-function">() =></span> { 1333 <span class="hljs-keyword">throw</span> <span class="hljs-keyword">new</span> <span class="hljs-title class_">TypeError</span>(<span class="hljs-string">'Wrong value'</span>); 1334 }, 1335 <span class="hljs-title class_">TypeError</span>, 1336);</code><code class="language-js cjs"><span class="hljs-keyword">const</span> assert = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:assert/strict'</span>); 1337 1338assert.<span class="hljs-title function_">doesNotThrow</span>( 1339 <span class="hljs-function">() =></span> { 1340 <span class="hljs-keyword">throw</span> <span class="hljs-keyword">new</span> <span class="hljs-title class_">TypeError</span>(<span class="hljs-string">'Wrong value'</span>); 1341 }, 1342 <span class="hljs-title class_">TypeError</span>, 1343);</code><button class="copy-button">copy</button></pre> 1344<p>If an <a href="#class-assertassertionerror"><code>AssertionError</code></a> is thrown and a value is provided for the <code>message</code> 1345parameter, the value of <code>message</code> will be appended to the <a href="#class-assertassertionerror"><code>AssertionError</code></a> 1346message:</p> 1347 1348<pre class="with-45-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> assert <span class="hljs-keyword">from</span> <span class="hljs-string">'node:assert/strict'</span>; 1349 1350assert.<span class="hljs-title function_">doesNotThrow</span>( 1351 <span class="hljs-function">() =></span> { 1352 <span class="hljs-keyword">throw</span> <span class="hljs-keyword">new</span> <span class="hljs-title class_">TypeError</span>(<span class="hljs-string">'Wrong value'</span>); 1353 }, 1354 <span class="hljs-regexp">/Wrong value/</span>, 1355 <span class="hljs-string">'Whoops'</span>, 1356); 1357<span class="hljs-comment">// Throws: AssertionError: Got unwanted exception: Whoops</span></code><code class="language-js cjs"><span class="hljs-keyword">const</span> assert = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:assert/strict'</span>); 1358 1359assert.<span class="hljs-title function_">doesNotThrow</span>( 1360 <span class="hljs-function">() =></span> { 1361 <span class="hljs-keyword">throw</span> <span class="hljs-keyword">new</span> <span class="hljs-title class_">TypeError</span>(<span class="hljs-string">'Wrong value'</span>); 1362 }, 1363 <span class="hljs-regexp">/Wrong value/</span>, 1364 <span class="hljs-string">'Whoops'</span>, 1365); 1366<span class="hljs-comment">// Throws: AssertionError: Got unwanted exception: Whoops</span></code><button class="copy-button">copy</button></pre> 1367</section><section><h3><code>assert.equal(actual, expected[, message])</code><span><a class="mark" href="#assertequalactual-expected-message" id="assertequalactual-expected-message">#</a></span><a aria-hidden="true" class="legacy" id="assert_assert_equal_actual_expected_message"></a></h3> 1368<div class="api_metadata"> 1369<details class="changelog"><summary>History</summary> 1370<table> 1371<tbody><tr><th>Version</th><th>Changes</th></tr> 1372<tr><td>v16.0.0, v14.18.0</td> 1373<td><p>In Legacy assertion mode, changed status from Deprecated to Legacy.</p></td></tr> 1374<tr><td>v14.0.0</td> 1375<td><p>NaN is now treated as being identical if both sides are NaN.</p></td></tr> 1376<tr><td>v0.1.21</td> 1377<td><p><span>Added in: v0.1.21</span></p></td></tr> 1378</tbody></table> 1379</details> 1380</div> 1381<ul> 1382<li><code>actual</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 1383<li><code>expected</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 1384<li><code>message</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error" class="type"><Error></a></li> 1385</ul> 1386<p><strong>Strict assertion mode</strong></p> 1387<p>An alias of <a href="#assertstrictequalactual-expected-message"><code>assert.strictEqual()</code></a>.</p> 1388<p><strong>Legacy assertion mode</strong></p> 1389<p></p><div class="api_stability api_stability_3"><a href="documentation.html#stability-index">Stability: 3</a> - Legacy: Use <a href="#assertstrictequalactual-expected-message"><code>assert.strictEqual()</code></a> instead.</div><p></p> 1390<p>Tests shallow, coercive equality between the <code>actual</code> and <code>expected</code> parameters 1391using the <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Equality"><code>==</code> operator</a>. <code>NaN</code> is specially handled 1392and treated as being identical if both sides are <code>NaN</code>.</p> 1393 1394<pre class="with-38-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> assert <span class="hljs-keyword">from</span> <span class="hljs-string">'node:assert'</span>; 1395 1396assert.<span class="hljs-title function_">equal</span>(<span class="hljs-number">1</span>, <span class="hljs-number">1</span>); 1397<span class="hljs-comment">// OK, 1 == 1</span> 1398assert.<span class="hljs-title function_">equal</span>(<span class="hljs-number">1</span>, <span class="hljs-string">'1'</span>); 1399<span class="hljs-comment">// OK, 1 == '1'</span> 1400assert.<span class="hljs-title function_">equal</span>(<span class="hljs-title class_">NaN</span>, <span class="hljs-title class_">NaN</span>); 1401<span class="hljs-comment">// OK</span> 1402 1403assert.<span class="hljs-title function_">equal</span>(<span class="hljs-number">1</span>, <span class="hljs-number">2</span>); 1404<span class="hljs-comment">// AssertionError: 1 == 2</span> 1405assert.<span class="hljs-title function_">equal</span>({ <span class="hljs-attr">a</span>: { <span class="hljs-attr">b</span>: <span class="hljs-number">1</span> } }, { <span class="hljs-attr">a</span>: { <span class="hljs-attr">b</span>: <span class="hljs-number">1</span> } }); 1406<span class="hljs-comment">// AssertionError: { a: { b: 1 } } == { a: { b: 1 } }</span></code><code class="language-js cjs"><span class="hljs-keyword">const</span> assert = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:assert'</span>); 1407 1408assert.<span class="hljs-title function_">equal</span>(<span class="hljs-number">1</span>, <span class="hljs-number">1</span>); 1409<span class="hljs-comment">// OK, 1 == 1</span> 1410assert.<span class="hljs-title function_">equal</span>(<span class="hljs-number">1</span>, <span class="hljs-string">'1'</span>); 1411<span class="hljs-comment">// OK, 1 == '1'</span> 1412assert.<span class="hljs-title function_">equal</span>(<span class="hljs-title class_">NaN</span>, <span class="hljs-title class_">NaN</span>); 1413<span class="hljs-comment">// OK</span> 1414 1415assert.<span class="hljs-title function_">equal</span>(<span class="hljs-number">1</span>, <span class="hljs-number">2</span>); 1416<span class="hljs-comment">// AssertionError: 1 == 2</span> 1417assert.<span class="hljs-title function_">equal</span>({ <span class="hljs-attr">a</span>: { <span class="hljs-attr">b</span>: <span class="hljs-number">1</span> } }, { <span class="hljs-attr">a</span>: { <span class="hljs-attr">b</span>: <span class="hljs-number">1</span> } }); 1418<span class="hljs-comment">// AssertionError: { a: { b: 1 } } == { a: { b: 1 } }</span></code><button class="copy-button">copy</button></pre> 1419<p>If the values are not equal, an <a href="#class-assertassertionerror"><code>AssertionError</code></a> is thrown with a <code>message</code> 1420property set equal to the value of the <code>message</code> parameter. If the <code>message</code> 1421parameter is undefined, a default error message is assigned. If the <code>message</code> 1422parameter is an instance of an <a href="errors.html#class-error"><code>Error</code></a> then it will be thrown instead of the 1423<code>AssertionError</code>.</p> 1424</section><section><h3><code>assert.fail([message])</code><span><a class="mark" href="#assertfailmessage" id="assertfailmessage">#</a></span><a aria-hidden="true" class="legacy" id="assert_assert_fail_message"></a></h3> 1425<div class="api_metadata"> 1426<span>Added in: v0.1.21</span> 1427</div> 1428<ul> 1429<li><code>message</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error" class="type"><Error></a> <strong>Default:</strong> <code>'Failed'</code></li> 1430</ul> 1431<p>Throws an <a href="#class-assertassertionerror"><code>AssertionError</code></a> with the provided error message or a default 1432error message. If the <code>message</code> parameter is an instance of an <a href="errors.html#class-error"><code>Error</code></a> then 1433it will be thrown instead of the <a href="#class-assertassertionerror"><code>AssertionError</code></a>.</p> 1434 1435<pre class="with-45-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> assert <span class="hljs-keyword">from</span> <span class="hljs-string">'node:assert/strict'</span>; 1436 1437assert.<span class="hljs-title function_">fail</span>(); 1438<span class="hljs-comment">// AssertionError [ERR_ASSERTION]: Failed</span> 1439 1440assert.<span class="hljs-title function_">fail</span>(<span class="hljs-string">'boom'</span>); 1441<span class="hljs-comment">// AssertionError [ERR_ASSERTION]: boom</span> 1442 1443assert.<span class="hljs-title function_">fail</span>(<span class="hljs-keyword">new</span> <span class="hljs-title class_">TypeError</span>(<span class="hljs-string">'need array'</span>)); 1444<span class="hljs-comment">// TypeError: need array</span></code><code class="language-js cjs"><span class="hljs-keyword">const</span> assert = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:assert/strict'</span>); 1445 1446assert.<span class="hljs-title function_">fail</span>(); 1447<span class="hljs-comment">// AssertionError [ERR_ASSERTION]: Failed</span> 1448 1449assert.<span class="hljs-title function_">fail</span>(<span class="hljs-string">'boom'</span>); 1450<span class="hljs-comment">// AssertionError [ERR_ASSERTION]: boom</span> 1451 1452assert.<span class="hljs-title function_">fail</span>(<span class="hljs-keyword">new</span> <span class="hljs-title class_">TypeError</span>(<span class="hljs-string">'need array'</span>)); 1453<span class="hljs-comment">// TypeError: need array</span></code><button class="copy-button">copy</button></pre> 1454<p>Using <code>assert.fail()</code> with more than two arguments is possible but deprecated. 1455See below for further details.</p> 1456</section><section><h3><code>assert.fail(actual, expected[, message[, operator[, stackStartFn]]])</code><span><a class="mark" href="#assertfailactual-expected-message-operator-stackstartfn" id="assertfailactual-expected-message-operator-stackstartfn">#</a></span><a aria-hidden="true" class="legacy" id="assert_assert_fail_actual_expected_message_operator_stackstartfn"></a></h3> 1457<div class="api_metadata"> 1458<details class="changelog"><summary>History</summary> 1459<table> 1460<tbody><tr><th>Version</th><th>Changes</th></tr> 1461<tr><td>v10.0.0</td> 1462<td><p>Calling <code>assert.fail()</code> with more than one argument is deprecated and emits a warning.</p></td></tr> 1463<tr><td>v0.1.21</td> 1464<td><p><span>Added in: v0.1.21</span></p></td></tr> 1465</tbody></table> 1466</details> 1467</div> 1468<p></p><div class="api_stability api_stability_0"><a href="documentation.html#stability-index">Stability: 0</a> - Deprecated: Use <code>assert.fail([message])</code> or other assert 1469functions instead.</div><p></p> 1470<ul> 1471<li><code>actual</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 1472<li><code>expected</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 1473<li><code>message</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error" class="type"><Error></a></li> 1474<li><code>operator</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> <strong>Default:</strong> <code>'!='</code></li> 1475<li><code>stackStartFn</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> <strong>Default:</strong> <code>assert.fail</code></li> 1476</ul> 1477<p>If <code>message</code> is falsy, the error message is set as the values of <code>actual</code> and 1478<code>expected</code> separated by the provided <code>operator</code>. If just the two <code>actual</code> and 1479<code>expected</code> arguments are provided, <code>operator</code> will default to <code>'!='</code>. If 1480<code>message</code> is provided as third argument it will be used as the error message and 1481the other arguments will be stored as properties on the thrown object. If 1482<code>stackStartFn</code> is provided, all stack frames above that function will be 1483removed from stacktrace (see <a href="errors.html#errorcapturestacktracetargetobject-constructoropt"><code>Error.captureStackTrace</code></a>). If no arguments are 1484given, the default message <code>Failed</code> will be used.</p> 1485 1486<pre class="with-45-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> assert <span class="hljs-keyword">from</span> <span class="hljs-string">'node:assert/strict'</span>; 1487 1488assert.<span class="hljs-title function_">fail</span>(<span class="hljs-string">'a'</span>, <span class="hljs-string">'b'</span>); 1489<span class="hljs-comment">// AssertionError [ERR_ASSERTION]: 'a' != 'b'</span> 1490 1491assert.<span class="hljs-title function_">fail</span>(<span class="hljs-number">1</span>, <span class="hljs-number">2</span>, <span class="hljs-literal">undefined</span>, <span class="hljs-string">'>'</span>); 1492<span class="hljs-comment">// AssertionError [ERR_ASSERTION]: 1 > 2</span> 1493 1494assert.<span class="hljs-title function_">fail</span>(<span class="hljs-number">1</span>, <span class="hljs-number">2</span>, <span class="hljs-string">'fail'</span>); 1495<span class="hljs-comment">// AssertionError [ERR_ASSERTION]: fail</span> 1496 1497assert.<span class="hljs-title function_">fail</span>(<span class="hljs-number">1</span>, <span class="hljs-number">2</span>, <span class="hljs-string">'whoops'</span>, <span class="hljs-string">'>'</span>); 1498<span class="hljs-comment">// AssertionError [ERR_ASSERTION]: whoops</span> 1499 1500assert.<span class="hljs-title function_">fail</span>(<span class="hljs-number">1</span>, <span class="hljs-number">2</span>, <span class="hljs-keyword">new</span> <span class="hljs-title class_">TypeError</span>(<span class="hljs-string">'need array'</span>)); 1501<span class="hljs-comment">// TypeError: need array</span></code><code class="language-js cjs"><span class="hljs-keyword">const</span> assert = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:assert/strict'</span>); 1502 1503assert.<span class="hljs-title function_">fail</span>(<span class="hljs-string">'a'</span>, <span class="hljs-string">'b'</span>); 1504<span class="hljs-comment">// AssertionError [ERR_ASSERTION]: 'a' != 'b'</span> 1505 1506assert.<span class="hljs-title function_">fail</span>(<span class="hljs-number">1</span>, <span class="hljs-number">2</span>, <span class="hljs-literal">undefined</span>, <span class="hljs-string">'>'</span>); 1507<span class="hljs-comment">// AssertionError [ERR_ASSERTION]: 1 > 2</span> 1508 1509assert.<span class="hljs-title function_">fail</span>(<span class="hljs-number">1</span>, <span class="hljs-number">2</span>, <span class="hljs-string">'fail'</span>); 1510<span class="hljs-comment">// AssertionError [ERR_ASSERTION]: fail</span> 1511 1512assert.<span class="hljs-title function_">fail</span>(<span class="hljs-number">1</span>, <span class="hljs-number">2</span>, <span class="hljs-string">'whoops'</span>, <span class="hljs-string">'>'</span>); 1513<span class="hljs-comment">// AssertionError [ERR_ASSERTION]: whoops</span> 1514 1515assert.<span class="hljs-title function_">fail</span>(<span class="hljs-number">1</span>, <span class="hljs-number">2</span>, <span class="hljs-keyword">new</span> <span class="hljs-title class_">TypeError</span>(<span class="hljs-string">'need array'</span>)); 1516<span class="hljs-comment">// TypeError: need array</span></code><button class="copy-button">copy</button></pre> 1517<p>In the last three cases <code>actual</code>, <code>expected</code>, and <code>operator</code> have no 1518influence on the error message.</p> 1519<p>Example use of <code>stackStartFn</code> for truncating the exception's stacktrace:</p> 1520 1521<pre class="with-45-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> assert <span class="hljs-keyword">from</span> <span class="hljs-string">'node:assert/strict'</span>; 1522 1523<span class="hljs-keyword">function</span> <span class="hljs-title function_">suppressFrame</span>(<span class="hljs-params"></span>) { 1524 assert.<span class="hljs-title function_">fail</span>(<span class="hljs-string">'a'</span>, <span class="hljs-string">'b'</span>, <span class="hljs-literal">undefined</span>, <span class="hljs-string">'!=='</span>, suppressFrame); 1525} 1526<span class="hljs-title function_">suppressFrame</span>(); 1527<span class="hljs-comment">// AssertionError [ERR_ASSERTION]: 'a' !== 'b'</span> 1528<span class="hljs-comment">// at repl:1:1</span> 1529<span class="hljs-comment">// at ContextifyScript.Script.runInThisContext (vm.js:44:33)</span> 1530<span class="hljs-comment">// ...</span></code><code class="language-js cjs"><span class="hljs-keyword">const</span> assert = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:assert/strict'</span>); 1531 1532<span class="hljs-keyword">function</span> <span class="hljs-title function_">suppressFrame</span>(<span class="hljs-params"></span>) { 1533 assert.<span class="hljs-title function_">fail</span>(<span class="hljs-string">'a'</span>, <span class="hljs-string">'b'</span>, <span class="hljs-literal">undefined</span>, <span class="hljs-string">'!=='</span>, suppressFrame); 1534} 1535<span class="hljs-title function_">suppressFrame</span>(); 1536<span class="hljs-comment">// AssertionError [ERR_ASSERTION]: 'a' !== 'b'</span> 1537<span class="hljs-comment">// at repl:1:1</span> 1538<span class="hljs-comment">// at ContextifyScript.Script.runInThisContext (vm.js:44:33)</span> 1539<span class="hljs-comment">// ...</span></code><button class="copy-button">copy</button></pre> 1540</section><section><h3><code>assert.ifError(value)</code><span><a class="mark" href="#assertiferrorvalue" id="assertiferrorvalue">#</a></span><a aria-hidden="true" class="legacy" id="assert_assert_iferror_value"></a></h3> 1541<div class="api_metadata"> 1542<details class="changelog"><summary>History</summary> 1543<table> 1544<tbody><tr><th>Version</th><th>Changes</th></tr> 1545<tr><td>v10.0.0</td> 1546<td><p>Instead of throwing the original error it is now wrapped into an [<code>AssertionError</code>][] that contains the full stack trace.</p></td></tr> 1547<tr><td>v10.0.0</td> 1548<td><p>Value may now only be <code>undefined</code> or <code>null</code>. Before all falsy values were handled the same as <code>null</code> and did not throw.</p></td></tr> 1549<tr><td>v0.1.97</td> 1550<td><p><span>Added in: v0.1.97</span></p></td></tr> 1551</tbody></table> 1552</details> 1553</div> 1554<ul> 1555<li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 1556</ul> 1557<p>Throws <code>value</code> if <code>value</code> is not <code>undefined</code> or <code>null</code>. This is useful when 1558testing the <code>error</code> argument in callbacks. The stack trace contains all frames 1559from the error passed to <code>ifError()</code> including the potential new frames for 1560<code>ifError()</code> itself.</p> 1561 1562<pre class="with-45-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> assert <span class="hljs-keyword">from</span> <span class="hljs-string">'node:assert/strict'</span>; 1563 1564assert.<span class="hljs-title function_">ifError</span>(<span class="hljs-literal">null</span>); 1565<span class="hljs-comment">// OK</span> 1566assert.<span class="hljs-title function_">ifError</span>(<span class="hljs-number">0</span>); 1567<span class="hljs-comment">// AssertionError [ERR_ASSERTION]: ifError got unwanted exception: 0</span> 1568assert.<span class="hljs-title function_">ifError</span>(<span class="hljs-string">'error'</span>); 1569<span class="hljs-comment">// AssertionError [ERR_ASSERTION]: ifError got unwanted exception: 'error'</span> 1570assert.<span class="hljs-title function_">ifError</span>(<span class="hljs-keyword">new</span> <span class="hljs-title class_">Error</span>()); 1571<span class="hljs-comment">// AssertionError [ERR_ASSERTION]: ifError got unwanted exception: Error</span> 1572 1573<span class="hljs-comment">// Create some random error frames.</span> 1574<span class="hljs-keyword">let</span> err; 1575(<span class="hljs-keyword">function</span> <span class="hljs-title function_">errorFrame</span>(<span class="hljs-params"></span>) { 1576 err = <span class="hljs-keyword">new</span> <span class="hljs-title class_">Error</span>(<span class="hljs-string">'test error'</span>); 1577})(); 1578 1579(<span class="hljs-keyword">function</span> <span class="hljs-title function_">ifErrorFrame</span>(<span class="hljs-params"></span>) { 1580 assert.<span class="hljs-title function_">ifError</span>(err); 1581})(); 1582<span class="hljs-comment">// AssertionError [ERR_ASSERTION]: ifError got unwanted exception: test error</span> 1583<span class="hljs-comment">// at ifErrorFrame</span> 1584<span class="hljs-comment">// at errorFrame</span></code><code class="language-js cjs"><span class="hljs-keyword">const</span> assert = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:assert/strict'</span>); 1585 1586assert.<span class="hljs-title function_">ifError</span>(<span class="hljs-literal">null</span>); 1587<span class="hljs-comment">// OK</span> 1588assert.<span class="hljs-title function_">ifError</span>(<span class="hljs-number">0</span>); 1589<span class="hljs-comment">// AssertionError [ERR_ASSERTION]: ifError got unwanted exception: 0</span> 1590assert.<span class="hljs-title function_">ifError</span>(<span class="hljs-string">'error'</span>); 1591<span class="hljs-comment">// AssertionError [ERR_ASSERTION]: ifError got unwanted exception: 'error'</span> 1592assert.<span class="hljs-title function_">ifError</span>(<span class="hljs-keyword">new</span> <span class="hljs-title class_">Error</span>()); 1593<span class="hljs-comment">// AssertionError [ERR_ASSERTION]: ifError got unwanted exception: Error</span> 1594 1595<span class="hljs-comment">// Create some random error frames.</span> 1596<span class="hljs-keyword">let</span> err; 1597(<span class="hljs-keyword">function</span> <span class="hljs-title function_">errorFrame</span>(<span class="hljs-params"></span>) { 1598 err = <span class="hljs-keyword">new</span> <span class="hljs-title class_">Error</span>(<span class="hljs-string">'test error'</span>); 1599})(); 1600 1601(<span class="hljs-keyword">function</span> <span class="hljs-title function_">ifErrorFrame</span>(<span class="hljs-params"></span>) { 1602 assert.<span class="hljs-title function_">ifError</span>(err); 1603})(); 1604<span class="hljs-comment">// AssertionError [ERR_ASSERTION]: ifError got unwanted exception: test error</span> 1605<span class="hljs-comment">// at ifErrorFrame</span> 1606<span class="hljs-comment">// at errorFrame</span></code><button class="copy-button">copy</button></pre> 1607</section><section><h3><code>assert.match(string, regexp[, message])</code><span><a class="mark" href="#assertmatchstring-regexp-message" id="assertmatchstring-regexp-message">#</a></span><a aria-hidden="true" class="legacy" id="assert_assert_match_string_regexp_message"></a></h3> 1608<div class="api_metadata"> 1609<details class="changelog"><summary>History</summary> 1610<table> 1611<tbody><tr><th>Version</th><th>Changes</th></tr> 1612<tr><td>v16.0.0</td> 1613<td><p>This API is no longer experimental.</p></td></tr> 1614<tr><td>v13.6.0, v12.16.0</td> 1615<td><p><span>Added in: v13.6.0, v12.16.0</span></p></td></tr> 1616</tbody></table> 1617</details> 1618</div> 1619<ul> 1620<li><code>string</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 1621<li><code>regexp</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/RegExp" class="type"><RegExp></a></li> 1622<li><code>message</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error" class="type"><Error></a></li> 1623</ul> 1624<p>Expects the <code>string</code> input to match the regular expression.</p> 1625 1626<pre class="with-45-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> assert <span class="hljs-keyword">from</span> <span class="hljs-string">'node:assert/strict'</span>; 1627 1628assert.<span class="hljs-title function_">match</span>(<span class="hljs-string">'I will fail'</span>, <span class="hljs-regexp">/pass/</span>); 1629<span class="hljs-comment">// AssertionError [ERR_ASSERTION]: The input did not match the regular ...</span> 1630 1631assert.<span class="hljs-title function_">match</span>(<span class="hljs-number">123</span>, <span class="hljs-regexp">/pass/</span>); 1632<span class="hljs-comment">// AssertionError [ERR_ASSERTION]: The "string" argument must be of type string.</span> 1633 1634assert.<span class="hljs-title function_">match</span>(<span class="hljs-string">'I will pass'</span>, <span class="hljs-regexp">/pass/</span>); 1635<span class="hljs-comment">// OK</span></code><code class="language-js cjs"><span class="hljs-keyword">const</span> assert = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:assert/strict'</span>); 1636 1637assert.<span class="hljs-title function_">match</span>(<span class="hljs-string">'I will fail'</span>, <span class="hljs-regexp">/pass/</span>); 1638<span class="hljs-comment">// AssertionError [ERR_ASSERTION]: The input did not match the regular ...</span> 1639 1640assert.<span class="hljs-title function_">match</span>(<span class="hljs-number">123</span>, <span class="hljs-regexp">/pass/</span>); 1641<span class="hljs-comment">// AssertionError [ERR_ASSERTION]: The "string" argument must be of type string.</span> 1642 1643assert.<span class="hljs-title function_">match</span>(<span class="hljs-string">'I will pass'</span>, <span class="hljs-regexp">/pass/</span>); 1644<span class="hljs-comment">// OK</span></code><button class="copy-button">copy</button></pre> 1645<p>If the values do not match, or if the <code>string</code> argument is of another type than 1646<code>string</code>, an <a href="#class-assertassertionerror"><code>AssertionError</code></a> is thrown with a <code>message</code> property set equal 1647to the value of the <code>message</code> parameter. If the <code>message</code> parameter is 1648undefined, a default error message is assigned. If the <code>message</code> parameter is an 1649instance of an <a href="errors.html#class-error"><code>Error</code></a> then it will be thrown instead of the 1650<a href="#class-assertassertionerror"><code>AssertionError</code></a>.</p> 1651</section><section><h3><code>assert.notDeepEqual(actual, expected[, message])</code><span><a class="mark" href="#assertnotdeepequalactual-expected-message" id="assertnotdeepequalactual-expected-message">#</a></span><a aria-hidden="true" class="legacy" id="assert_assert_notdeepequal_actual_expected_message"></a></h3> 1652<div class="api_metadata"> 1653<details class="changelog"><summary>History</summary> 1654<table> 1655<tbody><tr><th>Version</th><th>Changes</th></tr> 1656<tr><td>v16.0.0, v14.18.0</td> 1657<td><p>In Legacy assertion mode, changed status from Deprecated to Legacy.</p></td></tr> 1658<tr><td>v14.0.0</td> 1659<td><p>NaN is now treated as being identical if both sides are NaN.</p></td></tr> 1660<tr><td>v9.0.0</td> 1661<td><p>The <code>Error</code> names and messages are now properly compared.</p></td></tr> 1662<tr><td>v8.0.0</td> 1663<td><p>The <code>Set</code> and <code>Map</code> content is also compared.</p></td></tr> 1664<tr><td>v6.4.0, v4.7.1</td> 1665<td><p>Typed array slices are handled correctly now.</p></td></tr> 1666<tr><td>v6.1.0, v4.5.0</td> 1667<td><p>Objects with circular references can be used as inputs now.</p></td></tr> 1668<tr><td>v5.10.1, v4.4.3</td> 1669<td><p>Handle non-<code>Uint8Array</code> typed arrays correctly.</p></td></tr> 1670<tr><td>v0.1.21</td> 1671<td><p><span>Added in: v0.1.21</span></p></td></tr> 1672</tbody></table> 1673</details> 1674</div> 1675<ul> 1676<li><code>actual</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 1677<li><code>expected</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 1678<li><code>message</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error" class="type"><Error></a></li> 1679</ul> 1680<p><strong>Strict assertion mode</strong></p> 1681<p>An alias of <a href="#assertnotdeepstrictequalactual-expected-message"><code>assert.notDeepStrictEqual()</code></a>.</p> 1682<p><strong>Legacy assertion mode</strong></p> 1683<p></p><div class="api_stability api_stability_3"><a href="documentation.html#stability-index">Stability: 3</a> - Legacy: Use <a href="#assertnotdeepstrictequalactual-expected-message"><code>assert.notDeepStrictEqual()</code></a> instead.</div><p></p> 1684<p>Tests for any deep inequality. Opposite of <a href="#assertdeepequalactual-expected-message"><code>assert.deepEqual()</code></a>.</p> 1685 1686<pre class="with-38-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> assert <span class="hljs-keyword">from</span> <span class="hljs-string">'node:assert'</span>; 1687 1688<span class="hljs-keyword">const</span> obj1 = { 1689 <span class="hljs-attr">a</span>: { 1690 <span class="hljs-attr">b</span>: <span class="hljs-number">1</span>, 1691 }, 1692}; 1693<span class="hljs-keyword">const</span> obj2 = { 1694 <span class="hljs-attr">a</span>: { 1695 <span class="hljs-attr">b</span>: <span class="hljs-number">2</span>, 1696 }, 1697}; 1698<span class="hljs-keyword">const</span> obj3 = { 1699 <span class="hljs-attr">a</span>: { 1700 <span class="hljs-attr">b</span>: <span class="hljs-number">1</span>, 1701 }, 1702}; 1703<span class="hljs-keyword">const</span> obj4 = <span class="hljs-title class_">Object</span>.<span class="hljs-title function_">create</span>(obj1); 1704 1705assert.<span class="hljs-title function_">notDeepEqual</span>(obj1, obj1); 1706<span class="hljs-comment">// AssertionError: { a: { b: 1 } } notDeepEqual { a: { b: 1 } }</span> 1707 1708assert.<span class="hljs-title function_">notDeepEqual</span>(obj1, obj2); 1709<span class="hljs-comment">// OK</span> 1710 1711assert.<span class="hljs-title function_">notDeepEqual</span>(obj1, obj3); 1712<span class="hljs-comment">// AssertionError: { a: { b: 1 } } notDeepEqual { a: { b: 1 } }</span> 1713 1714assert.<span class="hljs-title function_">notDeepEqual</span>(obj1, obj4); 1715<span class="hljs-comment">// OK</span></code><code class="language-js cjs"><span class="hljs-keyword">const</span> assert = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:assert'</span>); 1716 1717<span class="hljs-keyword">const</span> obj1 = { 1718 <span class="hljs-attr">a</span>: { 1719 <span class="hljs-attr">b</span>: <span class="hljs-number">1</span>, 1720 }, 1721}; 1722<span class="hljs-keyword">const</span> obj2 = { 1723 <span class="hljs-attr">a</span>: { 1724 <span class="hljs-attr">b</span>: <span class="hljs-number">2</span>, 1725 }, 1726}; 1727<span class="hljs-keyword">const</span> obj3 = { 1728 <span class="hljs-attr">a</span>: { 1729 <span class="hljs-attr">b</span>: <span class="hljs-number">1</span>, 1730 }, 1731}; 1732<span class="hljs-keyword">const</span> obj4 = <span class="hljs-title class_">Object</span>.<span class="hljs-title function_">create</span>(obj1); 1733 1734assert.<span class="hljs-title function_">notDeepEqual</span>(obj1, obj1); 1735<span class="hljs-comment">// AssertionError: { a: { b: 1 } } notDeepEqual { a: { b: 1 } }</span> 1736 1737assert.<span class="hljs-title function_">notDeepEqual</span>(obj1, obj2); 1738<span class="hljs-comment">// OK</span> 1739 1740assert.<span class="hljs-title function_">notDeepEqual</span>(obj1, obj3); 1741<span class="hljs-comment">// AssertionError: { a: { b: 1 } } notDeepEqual { a: { b: 1 } }</span> 1742 1743assert.<span class="hljs-title function_">notDeepEqual</span>(obj1, obj4); 1744<span class="hljs-comment">// OK</span></code><button class="copy-button">copy</button></pre> 1745<p>If the values are deeply equal, an <a href="#class-assertassertionerror"><code>AssertionError</code></a> is thrown with a 1746<code>message</code> property set equal to the value of the <code>message</code> parameter. If the 1747<code>message</code> parameter is undefined, a default error message is assigned. If the 1748<code>message</code> parameter is an instance of an <a href="errors.html#class-error"><code>Error</code></a> then it will be thrown 1749instead of the <code>AssertionError</code>.</p> 1750</section><section><h3><code>assert.notDeepStrictEqual(actual, expected[, message])</code><span><a class="mark" href="#assertnotdeepstrictequalactual-expected-message" id="assertnotdeepstrictequalactual-expected-message">#</a></span><a aria-hidden="true" class="legacy" id="assert_assert_notdeepstrictequal_actual_expected_message"></a></h3> 1751<div class="api_metadata"> 1752<details class="changelog"><summary>History</summary> 1753<table> 1754<tbody><tr><th>Version</th><th>Changes</th></tr> 1755<tr><td>v9.0.0</td> 1756<td><p>The <code>-0</code> and <code>+0</code> are not considered equal anymore.</p></td></tr> 1757<tr><td>v9.0.0</td> 1758<td><p>The <code>NaN</code> is now compared using the <a href="https://tc39.github.io/ecma262/#sec-samevaluezero">SameValueZero</a> comparison.</p></td></tr> 1759<tr><td>v9.0.0</td> 1760<td><p>The <code>Error</code> names and messages are now properly compared.</p></td></tr> 1761<tr><td>v8.0.0</td> 1762<td><p>The <code>Set</code> and <code>Map</code> content is also compared.</p></td></tr> 1763<tr><td>v6.1.0</td> 1764<td><p>Objects with circular references can be used as inputs now.</p></td></tr> 1765<tr><td>v6.4.0, v4.7.1</td> 1766<td><p>Typed array slices are handled correctly now.</p></td></tr> 1767<tr><td>v5.10.1, v4.4.3</td> 1768<td><p>Handle non-<code>Uint8Array</code> typed arrays correctly.</p></td></tr> 1769<tr><td>v1.2.0</td> 1770<td><p><span>Added in: v1.2.0</span></p></td></tr> 1771</tbody></table> 1772</details> 1773</div> 1774<ul> 1775<li><code>actual</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 1776<li><code>expected</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 1777<li><code>message</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error" class="type"><Error></a></li> 1778</ul> 1779<p>Tests for deep strict inequality. Opposite of <a href="#assertdeepstrictequalactual-expected-message"><code>assert.deepStrictEqual()</code></a>.</p> 1780 1781<pre class="with-45-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> assert <span class="hljs-keyword">from</span> <span class="hljs-string">'node:assert/strict'</span>; 1782 1783assert.<span class="hljs-title function_">notDeepStrictEqual</span>({ <span class="hljs-attr">a</span>: <span class="hljs-number">1</span> }, { <span class="hljs-attr">a</span>: <span class="hljs-string">'1'</span> }); 1784<span class="hljs-comment">// OK</span></code><code class="language-js cjs"><span class="hljs-keyword">const</span> assert = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:assert/strict'</span>); 1785 1786assert.<span class="hljs-title function_">notDeepStrictEqual</span>({ <span class="hljs-attr">a</span>: <span class="hljs-number">1</span> }, { <span class="hljs-attr">a</span>: <span class="hljs-string">'1'</span> }); 1787<span class="hljs-comment">// OK</span></code><button class="copy-button">copy</button></pre> 1788<p>If the values are deeply and strictly equal, an <a href="#class-assertassertionerror"><code>AssertionError</code></a> is thrown 1789with a <code>message</code> property set equal to the value of the <code>message</code> parameter. If 1790the <code>message</code> parameter is undefined, a default error message is assigned. If 1791the <code>message</code> parameter is an instance of an <a href="errors.html#class-error"><code>Error</code></a> then it will be thrown 1792instead of the <a href="#class-assertassertionerror"><code>AssertionError</code></a>.</p> 1793</section><section><h3><code>assert.notEqual(actual, expected[, message])</code><span><a class="mark" href="#assertnotequalactual-expected-message" id="assertnotequalactual-expected-message">#</a></span><a aria-hidden="true" class="legacy" id="assert_assert_notequal_actual_expected_message"></a></h3> 1794<div class="api_metadata"> 1795<details class="changelog"><summary>History</summary> 1796<table> 1797<tbody><tr><th>Version</th><th>Changes</th></tr> 1798<tr><td>v16.0.0, v14.18.0</td> 1799<td><p>In Legacy assertion mode, changed status from Deprecated to Legacy.</p></td></tr> 1800<tr><td>v14.0.0</td> 1801<td><p>NaN is now treated as being identical if both sides are NaN.</p></td></tr> 1802<tr><td>v0.1.21</td> 1803<td><p><span>Added in: v0.1.21</span></p></td></tr> 1804</tbody></table> 1805</details> 1806</div> 1807<ul> 1808<li><code>actual</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 1809<li><code>expected</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 1810<li><code>message</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error" class="type"><Error></a></li> 1811</ul> 1812<p><strong>Strict assertion mode</strong></p> 1813<p>An alias of <a href="#assertnotstrictequalactual-expected-message"><code>assert.notStrictEqual()</code></a>.</p> 1814<p><strong>Legacy assertion mode</strong></p> 1815<p></p><div class="api_stability api_stability_3"><a href="documentation.html#stability-index">Stability: 3</a> - Legacy: Use <a href="#assertnotstrictequalactual-expected-message"><code>assert.notStrictEqual()</code></a> instead.</div><p></p> 1816<p>Tests shallow, coercive inequality with the <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Inequality"><code>!=</code> operator</a>. <code>NaN</code> is 1817specially handled and treated as being identical if both sides are <code>NaN</code>.</p> 1818 1819<pre class="with-38-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> assert <span class="hljs-keyword">from</span> <span class="hljs-string">'node:assert'</span>; 1820 1821assert.<span class="hljs-title function_">notEqual</span>(<span class="hljs-number">1</span>, <span class="hljs-number">2</span>); 1822<span class="hljs-comment">// OK</span> 1823 1824assert.<span class="hljs-title function_">notEqual</span>(<span class="hljs-number">1</span>, <span class="hljs-number">1</span>); 1825<span class="hljs-comment">// AssertionError: 1 != 1</span> 1826 1827assert.<span class="hljs-title function_">notEqual</span>(<span class="hljs-number">1</span>, <span class="hljs-string">'1'</span>); 1828<span class="hljs-comment">// AssertionError: 1 != '1'</span></code><code class="language-js cjs"><span class="hljs-keyword">const</span> assert = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:assert'</span>); 1829 1830assert.<span class="hljs-title function_">notEqual</span>(<span class="hljs-number">1</span>, <span class="hljs-number">2</span>); 1831<span class="hljs-comment">// OK</span> 1832 1833assert.<span class="hljs-title function_">notEqual</span>(<span class="hljs-number">1</span>, <span class="hljs-number">1</span>); 1834<span class="hljs-comment">// AssertionError: 1 != 1</span> 1835 1836assert.<span class="hljs-title function_">notEqual</span>(<span class="hljs-number">1</span>, <span class="hljs-string">'1'</span>); 1837<span class="hljs-comment">// AssertionError: 1 != '1'</span></code><button class="copy-button">copy</button></pre> 1838<p>If the values are equal, an <a href="#class-assertassertionerror"><code>AssertionError</code></a> is thrown with a <code>message</code> 1839property set equal to the value of the <code>message</code> parameter. If the <code>message</code> 1840parameter is undefined, a default error message is assigned. If the <code>message</code> 1841parameter is an instance of an <a href="errors.html#class-error"><code>Error</code></a> then it will be thrown instead of the 1842<code>AssertionError</code>.</p> 1843</section><section><h3><code>assert.notStrictEqual(actual, expected[, message])</code><span><a class="mark" href="#assertnotstrictequalactual-expected-message" id="assertnotstrictequalactual-expected-message">#</a></span><a aria-hidden="true" class="legacy" id="assert_assert_notstrictequal_actual_expected_message"></a></h3> 1844<div class="api_metadata"> 1845<details class="changelog"><summary>History</summary> 1846<table> 1847<tbody><tr><th>Version</th><th>Changes</th></tr> 1848<tr><td>v10.0.0</td> 1849<td><p>Used comparison changed from Strict Equality to <code>Object.is()</code>.</p></td></tr> 1850<tr><td>v0.1.21</td> 1851<td><p><span>Added in: v0.1.21</span></p></td></tr> 1852</tbody></table> 1853</details> 1854</div> 1855<ul> 1856<li><code>actual</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 1857<li><code>expected</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 1858<li><code>message</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error" class="type"><Error></a></li> 1859</ul> 1860<p>Tests strict inequality between the <code>actual</code> and <code>expected</code> parameters as 1861determined by <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/is"><code>Object.is()</code></a>.</p> 1862 1863<pre class="with-45-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> assert <span class="hljs-keyword">from</span> <span class="hljs-string">'node:assert/strict'</span>; 1864 1865assert.<span class="hljs-title function_">notStrictEqual</span>(<span class="hljs-number">1</span>, <span class="hljs-number">2</span>); 1866<span class="hljs-comment">// OK</span> 1867 1868assert.<span class="hljs-title function_">notStrictEqual</span>(<span class="hljs-number">1</span>, <span class="hljs-number">1</span>); 1869<span class="hljs-comment">// AssertionError [ERR_ASSERTION]: Expected "actual" to be strictly unequal to:</span> 1870<span class="hljs-comment">//</span> 1871<span class="hljs-comment">// 1</span> 1872 1873assert.<span class="hljs-title function_">notStrictEqual</span>(<span class="hljs-number">1</span>, <span class="hljs-string">'1'</span>); 1874<span class="hljs-comment">// OK</span></code><code class="language-js cjs"><span class="hljs-keyword">const</span> assert = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:assert/strict'</span>); 1875 1876assert.<span class="hljs-title function_">notStrictEqual</span>(<span class="hljs-number">1</span>, <span class="hljs-number">2</span>); 1877<span class="hljs-comment">// OK</span> 1878 1879assert.<span class="hljs-title function_">notStrictEqual</span>(<span class="hljs-number">1</span>, <span class="hljs-number">1</span>); 1880<span class="hljs-comment">// AssertionError [ERR_ASSERTION]: Expected "actual" to be strictly unequal to:</span> 1881<span class="hljs-comment">//</span> 1882<span class="hljs-comment">// 1</span> 1883 1884assert.<span class="hljs-title function_">notStrictEqual</span>(<span class="hljs-number">1</span>, <span class="hljs-string">'1'</span>); 1885<span class="hljs-comment">// OK</span></code><button class="copy-button">copy</button></pre> 1886<p>If the values are strictly equal, an <a href="#class-assertassertionerror"><code>AssertionError</code></a> is thrown with a 1887<code>message</code> property set equal to the value of the <code>message</code> parameter. If the 1888<code>message</code> parameter is undefined, a default error message is assigned. If the 1889<code>message</code> parameter is an instance of an <a href="errors.html#class-error"><code>Error</code></a> then it will be thrown 1890instead of the <code>AssertionError</code>.</p> 1891</section><section><h3><code>assert.ok(value[, message])</code><span><a class="mark" href="#assertokvalue-message" id="assertokvalue-message">#</a></span><a aria-hidden="true" class="legacy" id="assert_assert_ok_value_message"></a></h3> 1892<div class="api_metadata"> 1893<details class="changelog"><summary>History</summary> 1894<table> 1895<tbody><tr><th>Version</th><th>Changes</th></tr> 1896<tr><td>v10.0.0</td> 1897<td><p>The <code>assert.ok()</code> (no arguments) will now use a predefined error message.</p></td></tr> 1898<tr><td>v0.1.21</td> 1899<td><p><span>Added in: v0.1.21</span></p></td></tr> 1900</tbody></table> 1901</details> 1902</div> 1903<ul> 1904<li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 1905<li><code>message</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error" class="type"><Error></a></li> 1906</ul> 1907<p>Tests if <code>value</code> is truthy. It is equivalent to 1908<code>assert.equal(!!value, true, message)</code>.</p> 1909<p>If <code>value</code> is not truthy, an <a href="#class-assertassertionerror"><code>AssertionError</code></a> is thrown with a <code>message</code> 1910property set equal to the value of the <code>message</code> parameter. If the <code>message</code> 1911parameter is <code>undefined</code>, a default error message is assigned. If the <code>message</code> 1912parameter is an instance of an <a href="errors.html#class-error"><code>Error</code></a> then it will be thrown instead of the 1913<code>AssertionError</code>. 1914If no arguments are passed in at all <code>message</code> will be set to the string: 1915<code>'No value argument passed to `assert.ok()`'</code>.</p> 1916<p>Be aware that in the <code>repl</code> the error message will be different to the one 1917thrown in a file! See below for further details.</p> 1918 1919<pre class="with-45-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> assert <span class="hljs-keyword">from</span> <span class="hljs-string">'node:assert/strict'</span>; 1920 1921assert.<span class="hljs-title function_">ok</span>(<span class="hljs-literal">true</span>); 1922<span class="hljs-comment">// OK</span> 1923assert.<span class="hljs-title function_">ok</span>(<span class="hljs-number">1</span>); 1924<span class="hljs-comment">// OK</span> 1925 1926assert.<span class="hljs-title function_">ok</span>(); 1927<span class="hljs-comment">// AssertionError: No value argument passed to `assert.ok()`</span> 1928 1929assert.<span class="hljs-title function_">ok</span>(<span class="hljs-literal">false</span>, <span class="hljs-string">'it\'s false'</span>); 1930<span class="hljs-comment">// AssertionError: it's false</span> 1931 1932<span class="hljs-comment">// In the repl:</span> 1933assert.<span class="hljs-title function_">ok</span>(<span class="hljs-keyword">typeof</span> <span class="hljs-number">123</span> === <span class="hljs-string">'string'</span>); 1934<span class="hljs-comment">// AssertionError: false == true</span> 1935 1936<span class="hljs-comment">// In a file (e.g. test.js):</span> 1937assert.<span class="hljs-title function_">ok</span>(<span class="hljs-keyword">typeof</span> <span class="hljs-number">123</span> === <span class="hljs-string">'string'</span>); 1938<span class="hljs-comment">// AssertionError: The expression evaluated to a falsy value:</span> 1939<span class="hljs-comment">//</span> 1940<span class="hljs-comment">// assert.ok(typeof 123 === 'string')</span> 1941 1942assert.<span class="hljs-title function_">ok</span>(<span class="hljs-literal">false</span>); 1943<span class="hljs-comment">// AssertionError: The expression evaluated to a falsy value:</span> 1944<span class="hljs-comment">//</span> 1945<span class="hljs-comment">// assert.ok(false)</span> 1946 1947assert.<span class="hljs-title function_">ok</span>(<span class="hljs-number">0</span>); 1948<span class="hljs-comment">// AssertionError: The expression evaluated to a falsy value:</span> 1949<span class="hljs-comment">//</span> 1950<span class="hljs-comment">// assert.ok(0)</span></code><code class="language-js cjs"><span class="hljs-keyword">const</span> assert = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:assert/strict'</span>); 1951 1952assert.<span class="hljs-title function_">ok</span>(<span class="hljs-literal">true</span>); 1953<span class="hljs-comment">// OK</span> 1954assert.<span class="hljs-title function_">ok</span>(<span class="hljs-number">1</span>); 1955<span class="hljs-comment">// OK</span> 1956 1957assert.<span class="hljs-title function_">ok</span>(); 1958<span class="hljs-comment">// AssertionError: No value argument passed to `assert.ok()`</span> 1959 1960assert.<span class="hljs-title function_">ok</span>(<span class="hljs-literal">false</span>, <span class="hljs-string">'it\'s false'</span>); 1961<span class="hljs-comment">// AssertionError: it's false</span> 1962 1963<span class="hljs-comment">// In the repl:</span> 1964assert.<span class="hljs-title function_">ok</span>(<span class="hljs-keyword">typeof</span> <span class="hljs-number">123</span> === <span class="hljs-string">'string'</span>); 1965<span class="hljs-comment">// AssertionError: false == true</span> 1966 1967<span class="hljs-comment">// In a file (e.g. test.js):</span> 1968assert.<span class="hljs-title function_">ok</span>(<span class="hljs-keyword">typeof</span> <span class="hljs-number">123</span> === <span class="hljs-string">'string'</span>); 1969<span class="hljs-comment">// AssertionError: The expression evaluated to a falsy value:</span> 1970<span class="hljs-comment">//</span> 1971<span class="hljs-comment">// assert.ok(typeof 123 === 'string')</span> 1972 1973assert.<span class="hljs-title function_">ok</span>(<span class="hljs-literal">false</span>); 1974<span class="hljs-comment">// AssertionError: The expression evaluated to a falsy value:</span> 1975<span class="hljs-comment">//</span> 1976<span class="hljs-comment">// assert.ok(false)</span> 1977 1978assert.<span class="hljs-title function_">ok</span>(<span class="hljs-number">0</span>); 1979<span class="hljs-comment">// AssertionError: The expression evaluated to a falsy value:</span> 1980<span class="hljs-comment">//</span> 1981<span class="hljs-comment">// assert.ok(0)</span></code><button class="copy-button">copy</button></pre> 1982 1983<pre class="with-40-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> assert <span class="hljs-keyword">from</span> <span class="hljs-string">'node:assert/strict'</span>; 1984 1985<span class="hljs-comment">// Using `assert()` works the same:</span> 1986<span class="hljs-title function_">assert</span>(<span class="hljs-number">0</span>); 1987<span class="hljs-comment">// AssertionError: The expression evaluated to a falsy value:</span> 1988<span class="hljs-comment">//</span> 1989<span class="hljs-comment">// assert(0)</span></code><code class="language-js cjs"><span class="hljs-keyword">const</span> assert = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:assert'</span>); 1990 1991<span class="hljs-comment">// Using `assert()` works the same:</span> 1992<span class="hljs-title function_">assert</span>(<span class="hljs-number">0</span>); 1993<span class="hljs-comment">// AssertionError: The expression evaluated to a falsy value:</span> 1994<span class="hljs-comment">//</span> 1995<span class="hljs-comment">// assert(0)</span></code><button class="copy-button">copy</button></pre> 1996</section><section><h3><code>assert.rejects(asyncFn[, error][, message])</code><span><a class="mark" href="#assertrejectsasyncfn-error-message" id="assertrejectsasyncfn-error-message">#</a></span><a aria-hidden="true" class="legacy" id="assert_assert_rejects_asyncfn_error_message"></a></h3> 1997<div class="api_metadata"> 1998<span>Added in: v10.0.0</span> 1999</div> 2000<ul> 2001<li><code>asyncFn</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise" class="type"><Promise></a></li> 2002<li><code>error</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/RegExp" class="type"><RegExp></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error" class="type"><Error></a></li> 2003<li><code>message</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 2004</ul> 2005<p>Awaits the <code>asyncFn</code> promise or, if <code>asyncFn</code> is a function, immediately 2006calls the function and awaits the returned promise to complete. It will then 2007check that the promise is rejected.</p> 2008<p>If <code>asyncFn</code> is a function and it throws an error synchronously, 2009<code>assert.rejects()</code> will return a rejected <code>Promise</code> with that error. If the 2010function does not return a promise, <code>assert.rejects()</code> will return a rejected 2011<code>Promise</code> with an <a href="errors.html#err_invalid_return_value"><code>ERR_INVALID_RETURN_VALUE</code></a> error. In both cases the error 2012handler is skipped.</p> 2013<p>Besides the async nature to await the completion behaves identically to 2014<a href="#assertthrowsfn-error-message"><code>assert.throws()</code></a>.</p> 2015<p>If specified, <code>error</code> can be a <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Classes"><code>Class</code></a>, <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Regular_Expressions"><code>RegExp</code></a>, a validation function, 2016an object where each property will be tested for, or an instance of error where 2017each property will be tested for including the non-enumerable <code>message</code> and 2018<code>name</code> properties.</p> 2019<p>If specified, <code>message</code> will be the message provided by the <a href="#class-assertassertionerror"><code>AssertionError</code></a> 2020if the <code>asyncFn</code> fails to reject.</p> 2021 2022<pre class="with-45-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> assert <span class="hljs-keyword">from</span> <span class="hljs-string">'node:assert/strict'</span>; 2023 2024<span class="hljs-keyword">await</span> assert.<span class="hljs-title function_">rejects</span>( 2025 <span class="hljs-keyword">async</span> () => { 2026 <span class="hljs-keyword">throw</span> <span class="hljs-keyword">new</span> <span class="hljs-title class_">TypeError</span>(<span class="hljs-string">'Wrong value'</span>); 2027 }, 2028 { 2029 <span class="hljs-attr">name</span>: <span class="hljs-string">'TypeError'</span>, 2030 <span class="hljs-attr">message</span>: <span class="hljs-string">'Wrong value'</span>, 2031 }, 2032);</code><code class="language-js cjs"><span class="hljs-keyword">const</span> assert = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:assert/strict'</span>); 2033 2034(<span class="hljs-keyword">async</span> () => { 2035 <span class="hljs-keyword">await</span> assert.<span class="hljs-title function_">rejects</span>( 2036 <span class="hljs-keyword">async</span> () => { 2037 <span class="hljs-keyword">throw</span> <span class="hljs-keyword">new</span> <span class="hljs-title class_">TypeError</span>(<span class="hljs-string">'Wrong value'</span>); 2038 }, 2039 { 2040 <span class="hljs-attr">name</span>: <span class="hljs-string">'TypeError'</span>, 2041 <span class="hljs-attr">message</span>: <span class="hljs-string">'Wrong value'</span>, 2042 }, 2043 ); 2044})();</code><button class="copy-button">copy</button></pre> 2045 2046<pre class="with-45-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> assert <span class="hljs-keyword">from</span> <span class="hljs-string">'node:assert/strict'</span>; 2047 2048<span class="hljs-keyword">await</span> assert.<span class="hljs-title function_">rejects</span>( 2049 <span class="hljs-keyword">async</span> () => { 2050 <span class="hljs-keyword">throw</span> <span class="hljs-keyword">new</span> <span class="hljs-title class_">TypeError</span>(<span class="hljs-string">'Wrong value'</span>); 2051 }, 2052 <span class="hljs-function">(<span class="hljs-params">err</span>) =></span> { 2053 assert.<span class="hljs-title function_">strictEqual</span>(err.<span class="hljs-property">name</span>, <span class="hljs-string">'TypeError'</span>); 2054 assert.<span class="hljs-title function_">strictEqual</span>(err.<span class="hljs-property">message</span>, <span class="hljs-string">'Wrong value'</span>); 2055 <span class="hljs-keyword">return</span> <span class="hljs-literal">true</span>; 2056 }, 2057);</code><code class="language-js cjs"><span class="hljs-keyword">const</span> assert = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:assert/strict'</span>); 2058 2059(<span class="hljs-keyword">async</span> () => { 2060 <span class="hljs-keyword">await</span> assert.<span class="hljs-title function_">rejects</span>( 2061 <span class="hljs-keyword">async</span> () => { 2062 <span class="hljs-keyword">throw</span> <span class="hljs-keyword">new</span> <span class="hljs-title class_">TypeError</span>(<span class="hljs-string">'Wrong value'</span>); 2063 }, 2064 <span class="hljs-function">(<span class="hljs-params">err</span>) =></span> { 2065 assert.<span class="hljs-title function_">strictEqual</span>(err.<span class="hljs-property">name</span>, <span class="hljs-string">'TypeError'</span>); 2066 assert.<span class="hljs-title function_">strictEqual</span>(err.<span class="hljs-property">message</span>, <span class="hljs-string">'Wrong value'</span>); 2067 <span class="hljs-keyword">return</span> <span class="hljs-literal">true</span>; 2068 }, 2069 ); 2070})();</code><button class="copy-button">copy</button></pre> 2071 2072<pre class="with-45-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> assert <span class="hljs-keyword">from</span> <span class="hljs-string">'node:assert/strict'</span>; 2073 2074assert.<span class="hljs-title function_">rejects</span>( 2075 <span class="hljs-title class_">Promise</span>.<span class="hljs-title function_">reject</span>(<span class="hljs-keyword">new</span> <span class="hljs-title class_">Error</span>(<span class="hljs-string">'Wrong value'</span>)), 2076 <span class="hljs-title class_">Error</span>, 2077).<span class="hljs-title function_">then</span>(<span class="hljs-function">() =></span> { 2078 <span class="hljs-comment">// ...</span> 2079});</code><code class="language-js cjs"><span class="hljs-keyword">const</span> assert = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:assert/strict'</span>); 2080 2081assert.<span class="hljs-title function_">rejects</span>( 2082 <span class="hljs-title class_">Promise</span>.<span class="hljs-title function_">reject</span>(<span class="hljs-keyword">new</span> <span class="hljs-title class_">Error</span>(<span class="hljs-string">'Wrong value'</span>)), 2083 <span class="hljs-title class_">Error</span>, 2084).<span class="hljs-title function_">then</span>(<span class="hljs-function">() =></span> { 2085 <span class="hljs-comment">// ...</span> 2086});</code><button class="copy-button">copy</button></pre> 2087<p><code>error</code> cannot be a string. If a string is provided as the second 2088argument, then <code>error</code> is assumed to be omitted and the string will be used for 2089<code>message</code> instead. This can lead to easy-to-miss mistakes. Please read the 2090example in <a href="#assertthrowsfn-error-message"><code>assert.throws()</code></a> carefully if using a string as the second 2091argument gets considered.</p> 2092</section><section><h3><code>assert.strictEqual(actual, expected[, message])</code><span><a class="mark" href="#assertstrictequalactual-expected-message" id="assertstrictequalactual-expected-message">#</a></span><a aria-hidden="true" class="legacy" id="assert_assert_strictequal_actual_expected_message"></a></h3> 2093<div class="api_metadata"> 2094<details class="changelog"><summary>History</summary> 2095<table> 2096<tbody><tr><th>Version</th><th>Changes</th></tr> 2097<tr><td>v10.0.0</td> 2098<td><p>Used comparison changed from Strict Equality to <code>Object.is()</code>.</p></td></tr> 2099<tr><td>v0.1.21</td> 2100<td><p><span>Added in: v0.1.21</span></p></td></tr> 2101</tbody></table> 2102</details> 2103</div> 2104<ul> 2105<li><code>actual</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 2106<li><code>expected</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 2107<li><code>message</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error" class="type"><Error></a></li> 2108</ul> 2109<p>Tests strict equality between the <code>actual</code> and <code>expected</code> parameters as 2110determined by <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/is"><code>Object.is()</code></a>.</p> 2111 2112<pre class="with-45-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> assert <span class="hljs-keyword">from</span> <span class="hljs-string">'node:assert/strict'</span>; 2113 2114assert.<span class="hljs-title function_">strictEqual</span>(<span class="hljs-number">1</span>, <span class="hljs-number">2</span>); 2115<span class="hljs-comment">// AssertionError [ERR_ASSERTION]: Expected inputs to be strictly equal:</span> 2116<span class="hljs-comment">//</span> 2117<span class="hljs-comment">// 1 !== 2</span> 2118 2119assert.<span class="hljs-title function_">strictEqual</span>(<span class="hljs-number">1</span>, <span class="hljs-number">1</span>); 2120<span class="hljs-comment">// OK</span> 2121 2122assert.<span class="hljs-title function_">strictEqual</span>(<span class="hljs-string">'Hello foobar'</span>, <span class="hljs-string">'Hello World!'</span>); 2123<span class="hljs-comment">// AssertionError [ERR_ASSERTION]: Expected inputs to be strictly equal:</span> 2124<span class="hljs-comment">// + actual - expected</span> 2125<span class="hljs-comment">//</span> 2126<span class="hljs-comment">// + 'Hello foobar'</span> 2127<span class="hljs-comment">// - 'Hello World!'</span> 2128<span class="hljs-comment">// ^</span> 2129 2130<span class="hljs-keyword">const</span> apples = <span class="hljs-number">1</span>; 2131<span class="hljs-keyword">const</span> oranges = <span class="hljs-number">2</span>; 2132assert.<span class="hljs-title function_">strictEqual</span>(apples, oranges, <span class="hljs-string">`apples <span class="hljs-subst">${apples}</span> !== oranges <span class="hljs-subst">${oranges}</span>`</span>); 2133<span class="hljs-comment">// AssertionError [ERR_ASSERTION]: apples 1 !== oranges 2</span> 2134 2135assert.<span class="hljs-title function_">strictEqual</span>(<span class="hljs-number">1</span>, <span class="hljs-string">'1'</span>, <span class="hljs-keyword">new</span> <span class="hljs-title class_">TypeError</span>(<span class="hljs-string">'Inputs are not identical'</span>)); 2136<span class="hljs-comment">// TypeError: Inputs are not identical</span></code><code class="language-js cjs"><span class="hljs-keyword">const</span> assert = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:assert/strict'</span>); 2137 2138assert.<span class="hljs-title function_">strictEqual</span>(<span class="hljs-number">1</span>, <span class="hljs-number">2</span>); 2139<span class="hljs-comment">// AssertionError [ERR_ASSERTION]: Expected inputs to be strictly equal:</span> 2140<span class="hljs-comment">//</span> 2141<span class="hljs-comment">// 1 !== 2</span> 2142 2143assert.<span class="hljs-title function_">strictEqual</span>(<span class="hljs-number">1</span>, <span class="hljs-number">1</span>); 2144<span class="hljs-comment">// OK</span> 2145 2146assert.<span class="hljs-title function_">strictEqual</span>(<span class="hljs-string">'Hello foobar'</span>, <span class="hljs-string">'Hello World!'</span>); 2147<span class="hljs-comment">// AssertionError [ERR_ASSERTION]: Expected inputs to be strictly equal:</span> 2148<span class="hljs-comment">// + actual - expected</span> 2149<span class="hljs-comment">//</span> 2150<span class="hljs-comment">// + 'Hello foobar'</span> 2151<span class="hljs-comment">// - 'Hello World!'</span> 2152<span class="hljs-comment">// ^</span> 2153 2154<span class="hljs-keyword">const</span> apples = <span class="hljs-number">1</span>; 2155<span class="hljs-keyword">const</span> oranges = <span class="hljs-number">2</span>; 2156assert.<span class="hljs-title function_">strictEqual</span>(apples, oranges, <span class="hljs-string">`apples <span class="hljs-subst">${apples}</span> !== oranges <span class="hljs-subst">${oranges}</span>`</span>); 2157<span class="hljs-comment">// AssertionError [ERR_ASSERTION]: apples 1 !== oranges 2</span> 2158 2159assert.<span class="hljs-title function_">strictEqual</span>(<span class="hljs-number">1</span>, <span class="hljs-string">'1'</span>, <span class="hljs-keyword">new</span> <span class="hljs-title class_">TypeError</span>(<span class="hljs-string">'Inputs are not identical'</span>)); 2160<span class="hljs-comment">// TypeError: Inputs are not identical</span></code><button class="copy-button">copy</button></pre> 2161<p>If the values are not strictly equal, an <a href="#class-assertassertionerror"><code>AssertionError</code></a> is thrown with a 2162<code>message</code> property set equal to the value of the <code>message</code> parameter. If the 2163<code>message</code> parameter is undefined, a default error message is assigned. If the 2164<code>message</code> parameter is an instance of an <a href="errors.html#class-error"><code>Error</code></a> then it will be thrown 2165instead of the <a href="#class-assertassertionerror"><code>AssertionError</code></a>.</p> 2166</section><section><h3><code>assert.throws(fn[, error][, message])</code><span><a class="mark" href="#assertthrowsfn-error-message" id="assertthrowsfn-error-message">#</a></span><a aria-hidden="true" class="legacy" id="assert_assert_throws_fn_error_message"></a></h3> 2167<div class="api_metadata"> 2168<details class="changelog"><summary>History</summary> 2169<table> 2170<tbody><tr><th>Version</th><th>Changes</th></tr> 2171<tr><td>v10.2.0</td> 2172<td><p>The <code>error</code> parameter can be an object containing regular expressions now.</p></td></tr> 2173<tr><td>v9.9.0</td> 2174<td><p>The <code>error</code> parameter can now be an object as well.</p></td></tr> 2175<tr><td>v4.2.0</td> 2176<td><p>The <code>error</code> parameter can now be an arrow function.</p></td></tr> 2177<tr><td>v0.1.21</td> 2178<td><p><span>Added in: v0.1.21</span></p></td></tr> 2179</tbody></table> 2180</details> 2181</div> 2182<ul> 2183<li><code>fn</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a></li> 2184<li><code>error</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/RegExp" class="type"><RegExp></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error" class="type"><Error></a></li> 2185<li><code>message</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 2186</ul> 2187<p>Expects the function <code>fn</code> to throw an error.</p> 2188<p>If specified, <code>error</code> can be a <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Classes"><code>Class</code></a>, <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Regular_Expressions"><code>RegExp</code></a>, a validation function, 2189a validation object where each property will be tested for strict deep equality, 2190or an instance of error where each property will be tested for strict deep 2191equality including the non-enumerable <code>message</code> and <code>name</code> properties. When 2192using an object, it is also possible to use a regular expression, when 2193validating against a string property. See below for examples.</p> 2194<p>If specified, <code>message</code> will be appended to the message provided by the 2195<code>AssertionError</code> if the <code>fn</code> call fails to throw or in case the error validation 2196fails.</p> 2197<p>Custom validation object/error instance:</p> 2198 2199<pre class="with-45-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> assert <span class="hljs-keyword">from</span> <span class="hljs-string">'node:assert/strict'</span>; 2200 2201<span class="hljs-keyword">const</span> err = <span class="hljs-keyword">new</span> <span class="hljs-title class_">TypeError</span>(<span class="hljs-string">'Wrong value'</span>); 2202err.<span class="hljs-property">code</span> = <span class="hljs-number">404</span>; 2203err.<span class="hljs-property">foo</span> = <span class="hljs-string">'bar'</span>; 2204err.<span class="hljs-property">info</span> = { 2205 <span class="hljs-attr">nested</span>: <span class="hljs-literal">true</span>, 2206 <span class="hljs-attr">baz</span>: <span class="hljs-string">'text'</span>, 2207}; 2208err.<span class="hljs-property">reg</span> = <span class="hljs-regexp">/abc/i</span>; 2209 2210assert.<span class="hljs-title function_">throws</span>( 2211 <span class="hljs-function">() =></span> { 2212 <span class="hljs-keyword">throw</span> err; 2213 }, 2214 { 2215 <span class="hljs-attr">name</span>: <span class="hljs-string">'TypeError'</span>, 2216 <span class="hljs-attr">message</span>: <span class="hljs-string">'Wrong value'</span>, 2217 <span class="hljs-attr">info</span>: { 2218 <span class="hljs-attr">nested</span>: <span class="hljs-literal">true</span>, 2219 <span class="hljs-attr">baz</span>: <span class="hljs-string">'text'</span>, 2220 }, 2221 <span class="hljs-comment">// Only properties on the validation object will be tested for.</span> 2222 <span class="hljs-comment">// Using nested objects requires all properties to be present. Otherwise</span> 2223 <span class="hljs-comment">// the validation is going to fail.</span> 2224 }, 2225); 2226 2227<span class="hljs-comment">// Using regular expressions to validate error properties:</span> 2228assert.<span class="hljs-title function_">throws</span>( 2229 <span class="hljs-function">() =></span> { 2230 <span class="hljs-keyword">throw</span> err; 2231 }, 2232 { 2233 <span class="hljs-comment">// The `name` and `message` properties are strings and using regular</span> 2234 <span class="hljs-comment">// expressions on those will match against the string. If they fail, an</span> 2235 <span class="hljs-comment">// error is thrown.</span> 2236 <span class="hljs-attr">name</span>: <span class="hljs-regexp">/^TypeError$/</span>, 2237 <span class="hljs-attr">message</span>: <span class="hljs-regexp">/Wrong/</span>, 2238 <span class="hljs-attr">foo</span>: <span class="hljs-string">'bar'</span>, 2239 <span class="hljs-attr">info</span>: { 2240 <span class="hljs-attr">nested</span>: <span class="hljs-literal">true</span>, 2241 <span class="hljs-comment">// It is not possible to use regular expressions for nested properties!</span> 2242 <span class="hljs-attr">baz</span>: <span class="hljs-string">'text'</span>, 2243 }, 2244 <span class="hljs-comment">// The `reg` property contains a regular expression and only if the</span> 2245 <span class="hljs-comment">// validation object contains an identical regular expression, it is going</span> 2246 <span class="hljs-comment">// to pass.</span> 2247 <span class="hljs-attr">reg</span>: <span class="hljs-regexp">/abc/i</span>, 2248 }, 2249); 2250 2251<span class="hljs-comment">// Fails due to the different `message` and `name` properties:</span> 2252assert.<span class="hljs-title function_">throws</span>( 2253 <span class="hljs-function">() =></span> { 2254 <span class="hljs-keyword">const</span> otherErr = <span class="hljs-keyword">new</span> <span class="hljs-title class_">Error</span>(<span class="hljs-string">'Not found'</span>); 2255 <span class="hljs-comment">// Copy all enumerable properties from `err` to `otherErr`.</span> 2256 <span class="hljs-keyword">for</span> (<span class="hljs-keyword">const</span> [key, value] <span class="hljs-keyword">of</span> <span class="hljs-title class_">Object</span>.<span class="hljs-title function_">entries</span>(err)) { 2257 otherErr[key] = value; 2258 } 2259 <span class="hljs-keyword">throw</span> otherErr; 2260 }, 2261 <span class="hljs-comment">// The error's `message` and `name` properties will also be checked when using</span> 2262 <span class="hljs-comment">// an error as validation object.</span> 2263 err, 2264);</code><code class="language-js cjs"><span class="hljs-keyword">const</span> assert = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:assert/strict'</span>); 2265 2266<span class="hljs-keyword">const</span> err = <span class="hljs-keyword">new</span> <span class="hljs-title class_">TypeError</span>(<span class="hljs-string">'Wrong value'</span>); 2267err.<span class="hljs-property">code</span> = <span class="hljs-number">404</span>; 2268err.<span class="hljs-property">foo</span> = <span class="hljs-string">'bar'</span>; 2269err.<span class="hljs-property">info</span> = { 2270 <span class="hljs-attr">nested</span>: <span class="hljs-literal">true</span>, 2271 <span class="hljs-attr">baz</span>: <span class="hljs-string">'text'</span>, 2272}; 2273err.<span class="hljs-property">reg</span> = <span class="hljs-regexp">/abc/i</span>; 2274 2275assert.<span class="hljs-title function_">throws</span>( 2276 <span class="hljs-function">() =></span> { 2277 <span class="hljs-keyword">throw</span> err; 2278 }, 2279 { 2280 <span class="hljs-attr">name</span>: <span class="hljs-string">'TypeError'</span>, 2281 <span class="hljs-attr">message</span>: <span class="hljs-string">'Wrong value'</span>, 2282 <span class="hljs-attr">info</span>: { 2283 <span class="hljs-attr">nested</span>: <span class="hljs-literal">true</span>, 2284 <span class="hljs-attr">baz</span>: <span class="hljs-string">'text'</span>, 2285 }, 2286 <span class="hljs-comment">// Only properties on the validation object will be tested for.</span> 2287 <span class="hljs-comment">// Using nested objects requires all properties to be present. Otherwise</span> 2288 <span class="hljs-comment">// the validation is going to fail.</span> 2289 }, 2290); 2291 2292<span class="hljs-comment">// Using regular expressions to validate error properties:</span> 2293assert.<span class="hljs-title function_">throws</span>( 2294 <span class="hljs-function">() =></span> { 2295 <span class="hljs-keyword">throw</span> err; 2296 }, 2297 { 2298 <span class="hljs-comment">// The `name` and `message` properties are strings and using regular</span> 2299 <span class="hljs-comment">// expressions on those will match against the string. If they fail, an</span> 2300 <span class="hljs-comment">// error is thrown.</span> 2301 <span class="hljs-attr">name</span>: <span class="hljs-regexp">/^TypeError$/</span>, 2302 <span class="hljs-attr">message</span>: <span class="hljs-regexp">/Wrong/</span>, 2303 <span class="hljs-attr">foo</span>: <span class="hljs-string">'bar'</span>, 2304 <span class="hljs-attr">info</span>: { 2305 <span class="hljs-attr">nested</span>: <span class="hljs-literal">true</span>, 2306 <span class="hljs-comment">// It is not possible to use regular expressions for nested properties!</span> 2307 <span class="hljs-attr">baz</span>: <span class="hljs-string">'text'</span>, 2308 }, 2309 <span class="hljs-comment">// The `reg` property contains a regular expression and only if the</span> 2310 <span class="hljs-comment">// validation object contains an identical regular expression, it is going</span> 2311 <span class="hljs-comment">// to pass.</span> 2312 <span class="hljs-attr">reg</span>: <span class="hljs-regexp">/abc/i</span>, 2313 }, 2314); 2315 2316<span class="hljs-comment">// Fails due to the different `message` and `name` properties:</span> 2317assert.<span class="hljs-title function_">throws</span>( 2318 <span class="hljs-function">() =></span> { 2319 <span class="hljs-keyword">const</span> otherErr = <span class="hljs-keyword">new</span> <span class="hljs-title class_">Error</span>(<span class="hljs-string">'Not found'</span>); 2320 <span class="hljs-comment">// Copy all enumerable properties from `err` to `otherErr`.</span> 2321 <span class="hljs-keyword">for</span> (<span class="hljs-keyword">const</span> [key, value] <span class="hljs-keyword">of</span> <span class="hljs-title class_">Object</span>.<span class="hljs-title function_">entries</span>(err)) { 2322 otherErr[key] = value; 2323 } 2324 <span class="hljs-keyword">throw</span> otherErr; 2325 }, 2326 <span class="hljs-comment">// The error's `message` and `name` properties will also be checked when using</span> 2327 <span class="hljs-comment">// an error as validation object.</span> 2328 err, 2329);</code><button class="copy-button">copy</button></pre> 2330<p>Validate instanceof using constructor:</p> 2331 2332<pre class="with-45-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> assert <span class="hljs-keyword">from</span> <span class="hljs-string">'node:assert/strict'</span>; 2333 2334assert.<span class="hljs-title function_">throws</span>( 2335 <span class="hljs-function">() =></span> { 2336 <span class="hljs-keyword">throw</span> <span class="hljs-keyword">new</span> <span class="hljs-title class_">Error</span>(<span class="hljs-string">'Wrong value'</span>); 2337 }, 2338 <span class="hljs-title class_">Error</span>, 2339);</code><code class="language-js cjs"><span class="hljs-keyword">const</span> assert = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:assert/strict'</span>); 2340 2341assert.<span class="hljs-title function_">throws</span>( 2342 <span class="hljs-function">() =></span> { 2343 <span class="hljs-keyword">throw</span> <span class="hljs-keyword">new</span> <span class="hljs-title class_">Error</span>(<span class="hljs-string">'Wrong value'</span>); 2344 }, 2345 <span class="hljs-title class_">Error</span>, 2346);</code><button class="copy-button">copy</button></pre> 2347<p>Validate error message using <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Regular_Expressions"><code>RegExp</code></a>:</p> 2348<p>Using a regular expression runs <code>.toString</code> on the error object, and will 2349therefore also include the error name.</p> 2350 2351<pre class="with-45-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> assert <span class="hljs-keyword">from</span> <span class="hljs-string">'node:assert/strict'</span>; 2352 2353assert.<span class="hljs-title function_">throws</span>( 2354 <span class="hljs-function">() =></span> { 2355 <span class="hljs-keyword">throw</span> <span class="hljs-keyword">new</span> <span class="hljs-title class_">Error</span>(<span class="hljs-string">'Wrong value'</span>); 2356 }, 2357 <span class="hljs-regexp">/^Error: Wrong value$/</span>, 2358);</code><code class="language-js cjs"><span class="hljs-keyword">const</span> assert = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:assert/strict'</span>); 2359 2360assert.<span class="hljs-title function_">throws</span>( 2361 <span class="hljs-function">() =></span> { 2362 <span class="hljs-keyword">throw</span> <span class="hljs-keyword">new</span> <span class="hljs-title class_">Error</span>(<span class="hljs-string">'Wrong value'</span>); 2363 }, 2364 <span class="hljs-regexp">/^Error: Wrong value$/</span>, 2365);</code><button class="copy-button">copy</button></pre> 2366<p>Custom error validation:</p> 2367<p>The function must return <code>true</code> to indicate all internal validations passed. 2368It will otherwise fail with an <a href="#class-assertassertionerror"><code>AssertionError</code></a>.</p> 2369 2370<pre class="with-45-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> assert <span class="hljs-keyword">from</span> <span class="hljs-string">'node:assert/strict'</span>; 2371 2372assert.<span class="hljs-title function_">throws</span>( 2373 <span class="hljs-function">() =></span> { 2374 <span class="hljs-keyword">throw</span> <span class="hljs-keyword">new</span> <span class="hljs-title class_">Error</span>(<span class="hljs-string">'Wrong value'</span>); 2375 }, 2376 <span class="hljs-function">(<span class="hljs-params">err</span>) =></span> { 2377 <span class="hljs-title function_">assert</span>(err <span class="hljs-keyword">instanceof</span> <span class="hljs-title class_">Error</span>); 2378 <span class="hljs-title function_">assert</span>(<span class="hljs-regexp">/value/</span>.<span class="hljs-title function_">test</span>(err)); 2379 <span class="hljs-comment">// Avoid returning anything from validation functions besides `true`.</span> 2380 <span class="hljs-comment">// Otherwise, it's not clear what part of the validation failed. Instead,</span> 2381 <span class="hljs-comment">// throw an error about the specific validation that failed (as done in this</span> 2382 <span class="hljs-comment">// example) and add as much helpful debugging information to that error as</span> 2383 <span class="hljs-comment">// possible.</span> 2384 <span class="hljs-keyword">return</span> <span class="hljs-literal">true</span>; 2385 }, 2386 <span class="hljs-string">'unexpected error'</span>, 2387);</code><code class="language-js cjs"><span class="hljs-keyword">const</span> assert = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:assert/strict'</span>); 2388 2389assert.<span class="hljs-title function_">throws</span>( 2390 <span class="hljs-function">() =></span> { 2391 <span class="hljs-keyword">throw</span> <span class="hljs-keyword">new</span> <span class="hljs-title class_">Error</span>(<span class="hljs-string">'Wrong value'</span>); 2392 }, 2393 <span class="hljs-function">(<span class="hljs-params">err</span>) =></span> { 2394 <span class="hljs-title function_">assert</span>(err <span class="hljs-keyword">instanceof</span> <span class="hljs-title class_">Error</span>); 2395 <span class="hljs-title function_">assert</span>(<span class="hljs-regexp">/value/</span>.<span class="hljs-title function_">test</span>(err)); 2396 <span class="hljs-comment">// Avoid returning anything from validation functions besides `true`.</span> 2397 <span class="hljs-comment">// Otherwise, it's not clear what part of the validation failed. Instead,</span> 2398 <span class="hljs-comment">// throw an error about the specific validation that failed (as done in this</span> 2399 <span class="hljs-comment">// example) and add as much helpful debugging information to that error as</span> 2400 <span class="hljs-comment">// possible.</span> 2401 <span class="hljs-keyword">return</span> <span class="hljs-literal">true</span>; 2402 }, 2403 <span class="hljs-string">'unexpected error'</span>, 2404);</code><button class="copy-button">copy</button></pre> 2405<p><code>error</code> cannot be a string. If a string is provided as the second 2406argument, then <code>error</code> is assumed to be omitted and the string will be used for 2407<code>message</code> instead. This can lead to easy-to-miss mistakes. Using the same 2408message as the thrown error message is going to result in an 2409<code>ERR_AMBIGUOUS_ARGUMENT</code> error. Please read the example below carefully if using 2410a string as the second argument gets considered:</p> 2411 2412<pre class="with-45-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> assert <span class="hljs-keyword">from</span> <span class="hljs-string">'node:assert/strict'</span>; 2413 2414<span class="hljs-keyword">function</span> <span class="hljs-title function_">throwingFirst</span>(<span class="hljs-params"></span>) { 2415 <span class="hljs-keyword">throw</span> <span class="hljs-keyword">new</span> <span class="hljs-title class_">Error</span>(<span class="hljs-string">'First'</span>); 2416} 2417 2418<span class="hljs-keyword">function</span> <span class="hljs-title function_">throwingSecond</span>(<span class="hljs-params"></span>) { 2419 <span class="hljs-keyword">throw</span> <span class="hljs-keyword">new</span> <span class="hljs-title class_">Error</span>(<span class="hljs-string">'Second'</span>); 2420} 2421 2422<span class="hljs-keyword">function</span> <span class="hljs-title function_">notThrowing</span>(<span class="hljs-params"></span>) {} 2423 2424<span class="hljs-comment">// The second argument is a string and the input function threw an Error.</span> 2425<span class="hljs-comment">// The first case will not throw as it does not match for the error message</span> 2426<span class="hljs-comment">// thrown by the input function!</span> 2427assert.<span class="hljs-title function_">throws</span>(throwingFirst, <span class="hljs-string">'Second'</span>); 2428<span class="hljs-comment">// In the next example the message has no benefit over the message from the</span> 2429<span class="hljs-comment">// error and since it is not clear if the user intended to actually match</span> 2430<span class="hljs-comment">// against the error message, Node.js throws an `ERR_AMBIGUOUS_ARGUMENT` error.</span> 2431assert.<span class="hljs-title function_">throws</span>(throwingSecond, <span class="hljs-string">'Second'</span>); 2432<span class="hljs-comment">// TypeError [ERR_AMBIGUOUS_ARGUMENT]</span> 2433 2434<span class="hljs-comment">// The string is only used (as message) in case the function does not throw:</span> 2435assert.<span class="hljs-title function_">throws</span>(notThrowing, <span class="hljs-string">'Second'</span>); 2436<span class="hljs-comment">// AssertionError [ERR_ASSERTION]: Missing expected exception: Second</span> 2437 2438<span class="hljs-comment">// If it was intended to match for the error message do this instead:</span> 2439<span class="hljs-comment">// It does not throw because the error messages match.</span> 2440assert.<span class="hljs-title function_">throws</span>(throwingSecond, <span class="hljs-regexp">/Second$/</span>); 2441 2442<span class="hljs-comment">// If the error message does not match, an AssertionError is thrown.</span> 2443assert.<span class="hljs-title function_">throws</span>(throwingFirst, <span class="hljs-regexp">/Second$/</span>); 2444<span class="hljs-comment">// AssertionError [ERR_ASSERTION]</span></code><code class="language-js cjs"><span class="hljs-keyword">const</span> assert = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:assert/strict'</span>); 2445 2446<span class="hljs-keyword">function</span> <span class="hljs-title function_">throwingFirst</span>(<span class="hljs-params"></span>) { 2447 <span class="hljs-keyword">throw</span> <span class="hljs-keyword">new</span> <span class="hljs-title class_">Error</span>(<span class="hljs-string">'First'</span>); 2448} 2449 2450<span class="hljs-keyword">function</span> <span class="hljs-title function_">throwingSecond</span>(<span class="hljs-params"></span>) { 2451 <span class="hljs-keyword">throw</span> <span class="hljs-keyword">new</span> <span class="hljs-title class_">Error</span>(<span class="hljs-string">'Second'</span>); 2452} 2453 2454<span class="hljs-keyword">function</span> <span class="hljs-title function_">notThrowing</span>(<span class="hljs-params"></span>) {} 2455 2456<span class="hljs-comment">// The second argument is a string and the input function threw an Error.</span> 2457<span class="hljs-comment">// The first case will not throw as it does not match for the error message</span> 2458<span class="hljs-comment">// thrown by the input function!</span> 2459assert.<span class="hljs-title function_">throws</span>(throwingFirst, <span class="hljs-string">'Second'</span>); 2460<span class="hljs-comment">// In the next example the message has no benefit over the message from the</span> 2461<span class="hljs-comment">// error and since it is not clear if the user intended to actually match</span> 2462<span class="hljs-comment">// against the error message, Node.js throws an `ERR_AMBIGUOUS_ARGUMENT` error.</span> 2463assert.<span class="hljs-title function_">throws</span>(throwingSecond, <span class="hljs-string">'Second'</span>); 2464<span class="hljs-comment">// TypeError [ERR_AMBIGUOUS_ARGUMENT]</span> 2465 2466<span class="hljs-comment">// The string is only used (as message) in case the function does not throw:</span> 2467assert.<span class="hljs-title function_">throws</span>(notThrowing, <span class="hljs-string">'Second'</span>); 2468<span class="hljs-comment">// AssertionError [ERR_ASSERTION]: Missing expected exception: Second</span> 2469 2470<span class="hljs-comment">// If it was intended to match for the error message do this instead:</span> 2471<span class="hljs-comment">// It does not throw because the error messages match.</span> 2472assert.<span class="hljs-title function_">throws</span>(throwingSecond, <span class="hljs-regexp">/Second$/</span>); 2473 2474<span class="hljs-comment">// If the error message does not match, an AssertionError is thrown.</span> 2475assert.<span class="hljs-title function_">throws</span>(throwingFirst, <span class="hljs-regexp">/Second$/</span>); 2476<span class="hljs-comment">// AssertionError [ERR_ASSERTION]</span></code><button class="copy-button">copy</button></pre> 2477<p>Due to the confusing error-prone notation, avoid a string as the second 2478argument.</p></section> 2479 <!-- API END --> 2480 </div> 2481 </div> 2482 </div> 2483</body> 2484</html> 2485