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<!DOCTYPE html> <html lang="en"> <head> <meta charset="utf-8"> <meta name="viewport" content="width=device-width"> <meta name="nodejs.org:node-version" content="v16.20.0"> <title>Test runner | Node.js v16.20.0 Documentation</title> <link rel="stylesheet" href="https://fonts.googleapis.com/css?family=Lato:400,700,400italic&display=fallback"> <link rel="stylesheet" href="assets/style.css"> <link rel="stylesheet" href="assets/hljs.css"> <link rel="canonical" href="https://nodejs.org/api/test.html"> <script async defer src="assets/api.js" type="text/javascript"></script> <style>@media(max-width:494px){.with-34-chars>.js-flavor-selector{float:none;margin:0 0 1em auto;}}@media(max-width:454px){.with-29-chars>.js-flavor-selector{float:none;margin:0 0 1em auto;}}@media(max-width:590px){.with-46-chars>.js-flavor-selector{float:none;margin:0 0 1em auto;}}</style> </head> <body class="alt apidoc" id="api-section-test"> <div id="content" class="clearfix"> <div id="column2" class="interior"> <div 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contents </a> <div class="picker"><div class="toc"><ul> <li><span class="stability_1"><a href="#test-runner">Test runner</a></span> <ul> <li><a href="#subtests">Subtests</a></li> <li><a href="#skipping-tests">Skipping tests</a></li> <li><a href="#describeit-syntax"><code>describe</code>/<code>it</code> syntax</a> <ul> <li><a href="#only-tests"><code>only</code> tests</a></li> </ul> </li> <li><a href="#extraneous-asynchronous-activity">Extraneous asynchronous activity</a></li> <li><a href="#running-tests-from-the-command-line">Running tests from the command line</a> <ul> <li><a href="#test-runner-execution-model">Test runner execution model</a></li> </ul> </li> <li><a href="#runoptions"><code>run([options])</code></a></li> <li><a href="#testname-options-fn"><code>test([name][, options][, fn])</code></a></li> <li><a href="#describename-options-fn"><code>describe([name][, options][, fn])</code></a></li> <li><a href="#describeskipname-options-fn"><code>describe.skip([name][, options][, fn])</code></a></li> <li><a href="#describetodoname-options-fn"><code>describe.todo([name][, options][, fn])</code></a></li> <li><a href="#itname-options-fn"><code>it([name][, options][, fn])</code></a></li> <li><a href="#itskipname-options-fn"><code>it.skip([name][, options][, fn])</code></a></li> <li><a href="#ittodoname-options-fn"><code>it.todo([name][, options][, fn])</code></a></li> <li><a href="#before-fn-options"><code>before([, fn][, options])</code></a></li> <li><a href="#after-fn-options"><code>after([, fn][, options])</code></a></li> <li><a href="#beforeeach-fn-options"><code>beforeEach([, fn][, options])</code></a></li> <li><a href="#aftereach-fn-options"><code>afterEach([, fn][, options])</code></a></li> <li><a href="#class-tapstream">Class: <code>TapStream</code></a> <ul> <li><a href="#event-testdiagnostic">Event: <code>'test:diagnostic'</code></a></li> <li><a href="#event-testfail">Event: <code>'test:fail'</code></a></li> <li><a href="#event-testpass">Event: <code>'test:pass'</code></a></li> </ul> </li> <li><a href="#class-testcontext">Class: <code>TestContext</code></a> <ul> <li><a href="#contextbeforeeach-fn-options"><code>context.beforeEach([, fn][, options])</code></a></li> <li><a href="#contextaftereach-fn-options"><code>context.afterEach([, fn][, options])</code></a></li> <li><a href="#contextdiagnosticmessage"><code>context.diagnostic(message)</code></a></li> <li><a href="#contextname"><code>context.name</code></a></li> <li><a href="#contextrunonlyshouldrunonlytests"><code>context.runOnly(shouldRunOnlyTests)</code></a></li> <li><a href="#contextsignal"><code>context.signal</code></a></li> <li><a href="#contextskipmessage"><code>context.skip([message])</code></a></li> <li><a href="#contexttodomessage"><code>context.todo([message])</code></a></li> <li><a href="#contexttestname-options-fn"><code>context.test([name][, options][, fn])</code></a></li> </ul> </li> <li><a href="#class-suitecontext">Class: <code>SuiteContext</code></a> <ul> <li><a href="#contextname_1"><code>context.name</code></a></li> <li><a href="#contextsignal_1"><code>context.signal</code></a></li> </ul> </li> </ul> </li> </ul></div></div> </li> <li class="picker-header"> <a href="#"> <span class="collapsed-arrow">►</span><span class="expanded-arrow">▼</span> Index </a> <div class="picker"><ul> <li><a href="documentation.html" class="nav-documentation">About this documentation</a></li> <li><a href="synopsis.html" class="nav-synopsis">Usage and example</a></li> <li> <a href="index.html">Index</a> </li> </ul> <hr class="line"> <ul> <li><a href="assert.html" class="nav-assert">Assertion testing</a></li> <li><a href="async_context.html" class="nav-async_context">Asynchronous context tracking</a></li> <li><a href="async_hooks.html" class="nav-async_hooks">Async hooks</a></li> <li><a href="buffer.html" class="nav-buffer">Buffer</a></li> <li><a href="addons.html" class="nav-addons">C++ addons</a></li> <li><a href="n-api.html" class="nav-n-api">C/C++ addons with Node-API</a></li> <li><a href="embedding.html" class="nav-embedding">C++ embedder API</a></li> <li><a href="child_process.html" class="nav-child_process">Child processes</a></li> <li><a href="cluster.html" class="nav-cluster">Cluster</a></li> <li><a href="cli.html" class="nav-cli">Command-line options</a></li> <li><a href="console.html" class="nav-console">Console</a></li> <li><a href="corepack.html" class="nav-corepack">Corepack</a></li> <li><a href="crypto.html" class="nav-crypto">Crypto</a></li> <li><a href="debugger.html" class="nav-debugger">Debugger</a></li> <li><a href="deprecations.html" class="nav-deprecations">Deprecated APIs</a></li> <li><a href="diagnostics_channel.html" class="nav-diagnostics_channel">Diagnostics Channel</a></li> <li><a href="dns.html" class="nav-dns">DNS</a></li> <li><a href="domain.html" class="nav-domain">Domain</a></li> <li><a href="errors.html" class="nav-errors">Errors</a></li> <li><a href="events.html" class="nav-events">Events</a></li> <li><a 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href="https://nodejs.org/docs/latest-v18.x/api/test.html">18.x <b>LTS</b></a></li> <li><a href="https://nodejs.org/docs/latest-v17.x/api/test.html">17.x</a></li> <li><a href="https://nodejs.org/docs/latest-v16.x/api/test.html">16.x <b>LTS</b></a></li></ol></div> </li> <li class="picker-header"> <a href="#"> <span class="collapsed-arrow">►</span><span class="expanded-arrow">▼</span> Options </a> <div class="picker"> <ul> <li> <a href="all.html">View on single page</a> </li> <li> <a href="test.json">View as JSON</a> </li> <li class="edit_on_github"><a href="https://github.com/nodejs/node/edit/main/doc/api/test.md">Edit on GitHub</a></li> </ul> </div> </li> </ul> </div> <hr> </header> <details id="toc" open><summary>Table of contents</summary><ul> <li><span class="stability_1"><a href="#test-runner">Test runner</a></span> <ul> <li><a href="#subtests">Subtests</a></li> <li><a href="#skipping-tests">Skipping tests</a></li> <li><a href="#describeit-syntax"><code>describe</code>/<code>it</code> syntax</a> <ul> <li><a href="#only-tests"><code>only</code> tests</a></li> </ul> </li> <li><a href="#extraneous-asynchronous-activity">Extraneous asynchronous activity</a></li> <li><a href="#running-tests-from-the-command-line">Running tests from the command line</a> <ul> <li><a href="#test-runner-execution-model">Test runner execution model</a></li> </ul> </li> <li><a href="#runoptions"><code>run([options])</code></a></li> <li><a href="#testname-options-fn"><code>test([name][, options][, fn])</code></a></li> <li><a href="#describename-options-fn"><code>describe([name][, options][, fn])</code></a></li> <li><a href="#describeskipname-options-fn"><code>describe.skip([name][, options][, fn])</code></a></li> <li><a href="#describetodoname-options-fn"><code>describe.todo([name][, options][, fn])</code></a></li> <li><a href="#itname-options-fn"><code>it([name][, options][, fn])</code></a></li> <li><a href="#itskipname-options-fn"><code>it.skip([name][, options][, fn])</code></a></li> <li><a href="#ittodoname-options-fn"><code>it.todo([name][, options][, fn])</code></a></li> <li><a href="#before-fn-options"><code>before([, fn][, options])</code></a></li> <li><a href="#after-fn-options"><code>after([, fn][, options])</code></a></li> <li><a href="#beforeeach-fn-options"><code>beforeEach([, fn][, options])</code></a></li> <li><a href="#aftereach-fn-options"><code>afterEach([, fn][, options])</code></a></li> <li><a href="#class-tapstream">Class: <code>TapStream</code></a> <ul> <li><a href="#event-testdiagnostic">Event: <code>'test:diagnostic'</code></a></li> <li><a href="#event-testfail">Event: <code>'test:fail'</code></a></li> <li><a href="#event-testpass">Event: <code>'test:pass'</code></a></li> </ul> </li> <li><a href="#class-testcontext">Class: <code>TestContext</code></a> <ul> <li><a href="#contextbeforeeach-fn-options"><code>context.beforeEach([, fn][, options])</code></a></li> <li><a href="#contextaftereach-fn-options"><code>context.afterEach([, fn][, options])</code></a></li> <li><a href="#contextdiagnosticmessage"><code>context.diagnostic(message)</code></a></li> <li><a href="#contextname"><code>context.name</code></a></li> <li><a href="#contextrunonlyshouldrunonlytests"><code>context.runOnly(shouldRunOnlyTests)</code></a></li> <li><a href="#contextsignal"><code>context.signal</code></a></li> <li><a href="#contextskipmessage"><code>context.skip([message])</code></a></li> <li><a href="#contexttodomessage"><code>context.todo([message])</code></a></li> <li><a href="#contexttestname-options-fn"><code>context.test([name][, options][, fn])</code></a></li> </ul> </li> <li><a href="#class-suitecontext">Class: <code>SuiteContext</code></a> <ul> <li><a href="#contextname_1"><code>context.name</code></a></li> <li><a href="#contextsignal_1"><code>context.signal</code></a></li> </ul> </li> </ul> </li> </ul></details> <div id="apicontent"> <h2>Test runner<span><a class="mark" href="#test-runner" id="test-runner">#</a></span><a aria-hidden="true" class="legacy" id="test_test_runner"></a></h2> <p></p><div class="api_stability api_stability_1"><a href="documentation.html#stability-index">Stability: 1</a> - Experimental</div><p></p> <p><strong>Source Code:</strong> <a href="https://github.com/nodejs/node/blob/v16.20.0/lib/test.js">lib/test.js</a></p> <p>The <code>node:test</code> module facilitates the creation of JavaScript tests that report results in <a href="https://testanything.org/">TAP</a> format. To access it:</p> <pre class="with-34-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> test <span class="hljs-keyword">from</span> <span class="hljs-string">'node:test'</span>;</code><code class="language-js cjs"><span class="hljs-keyword">const</span> test = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:test'</span>);</code></pre> <p>This module is only available under the <code>node:</code> scheme. The following will not work:</p> <pre class="with-29-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> test <span class="hljs-keyword">from</span> <span class="hljs-string">'test'</span>;</code><code class="language-js cjs"><span class="hljs-keyword">const</span> test = <span class="hljs-built_in">require</span>(<span class="hljs-string">'test'</span>);</code></pre> <p>Tests created via the <code>test</code> module consist of a single function that is processed in one of three ways:</p> <ol> <li>A synchronous function that is considered failing if it throws an exception, and is considered passing otherwise.</li> <li>A function that returns a <code>Promise</code> that is considered failing if the <code>Promise</code> rejects, and is considered passing if the <code>Promise</code> resolves.</li> <li>A function that receives a callback function. If the callback receives any truthy value as its first argument, the test is considered failing. If a falsy value is passed as the first argument to the callback, the test is considered passing. If the test function receives a callback function and also returns a <code>Promise</code>, the test will fail.</li> </ol> <p>The following example illustrates how tests are written using the <code>test</code> module.</p> <pre><code class="language-js"><span class="hljs-title function_">test</span>(<span class="hljs-string">'synchronous passing test'</span>, <span class="hljs-function">(<span class="hljs-params">t</span>) =></span> { <span class="hljs-comment">// This test passes because it does not throw an exception.</span> assert.<span class="hljs-title function_">strictEqual</span>(<span class="hljs-number">1</span>, <span class="hljs-number">1</span>); }); <span class="hljs-title function_">test</span>(<span class="hljs-string">'synchronous failing test'</span>, <span class="hljs-function">(<span class="hljs-params">t</span>) =></span> { <span class="hljs-comment">// This test fails because it throws an exception.</span> assert.<span class="hljs-title function_">strictEqual</span>(<span class="hljs-number">1</span>, <span class="hljs-number">2</span>); }); <span class="hljs-title function_">test</span>(<span class="hljs-string">'asynchronous passing test'</span>, <span class="hljs-keyword">async</span> (t) => { <span class="hljs-comment">// This test passes because the Promise returned by the async</span> <span class="hljs-comment">// function is not rejected.</span> assert.<span class="hljs-title function_">strictEqual</span>(<span class="hljs-number">1</span>, <span class="hljs-number">1</span>); }); <span class="hljs-title function_">test</span>(<span class="hljs-string">'asynchronous failing test'</span>, <span class="hljs-keyword">async</span> (t) => { <span class="hljs-comment">// This test fails because the Promise returned by the async</span> <span class="hljs-comment">// function is rejected.</span> assert.<span class="hljs-title function_">strictEqual</span>(<span class="hljs-number">1</span>, <span class="hljs-number">2</span>); }); <span class="hljs-title function_">test</span>(<span class="hljs-string">'failing test using Promises'</span>, <span class="hljs-function">(<span class="hljs-params">t</span>) =></span> { <span class="hljs-comment">// Promises can be used directly as well.</span> <span class="hljs-keyword">return</span> <span class="hljs-keyword">new</span> <span class="hljs-title class_">Promise</span>(<span class="hljs-function">(<span class="hljs-params">resolve, reject</span>) =></span> { <span class="hljs-title function_">setImmediate</span>(<span class="hljs-function">() =></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">'this will cause the test to fail'</span>)); }); }); }); <span class="hljs-title function_">test</span>(<span class="hljs-string">'callback passing test'</span>, <span class="hljs-function">(<span class="hljs-params">t, done</span>) =></span> { <span class="hljs-comment">// done() is the callback function. When the setImmediate() runs, it invokes</span> <span class="hljs-comment">// done() with no arguments.</span> <span class="hljs-title function_">setImmediate</span>(done); }); <span class="hljs-title function_">test</span>(<span class="hljs-string">'callback failing test'</span>, <span class="hljs-function">(<span class="hljs-params">t, done</span>) =></span> { <span class="hljs-comment">// When the setImmediate() runs, done() is invoked with an Error object and</span> <span class="hljs-comment">// the test fails.</span> <span class="hljs-title function_">setImmediate</span>(<span class="hljs-function">() =></span> { <span class="hljs-title function_">done</span>(<span class="hljs-keyword">new</span> <span class="hljs-title class_">Error</span>(<span class="hljs-string">'callback failure'</span>)); }); });</code></pre> <p>As a test file executes, TAP is written to the standard output of the Node.js process. This output can be interpreted by any test harness that understands the TAP format. If any tests fail, the process exit code is set to <code>1</code>.</p> <section><h3>Subtests<span><a class="mark" href="#subtests" id="subtests">#</a></span><a aria-hidden="true" class="legacy" id="test_subtests"></a></h3> <p>The test context's <code>test()</code> method allows subtests to be created. This method behaves identically to the top level <code>test()</code> function. The following example demonstrates the creation of a top level test with two subtests.</p> <pre><code class="language-js"><span class="hljs-title function_">test</span>(<span class="hljs-string">'top level test'</span>, <span class="hljs-keyword">async</span> (t) => { <span class="hljs-keyword">await</span> t.<span class="hljs-title function_">test</span>(<span class="hljs-string">'subtest 1'</span>, <span class="hljs-function">(<span class="hljs-params">t</span>) =></span> { assert.<span class="hljs-title function_">strictEqual</span>(<span class="hljs-number">1</span>, <span class="hljs-number">1</span>); }); <span class="hljs-keyword">await</span> t.<span class="hljs-title function_">test</span>(<span class="hljs-string">'subtest 2'</span>, <span class="hljs-function">(<span class="hljs-params">t</span>) =></span> { assert.<span class="hljs-title function_">strictEqual</span>(<span class="hljs-number">2</span>, <span class="hljs-number">2</span>); }); });</code></pre> <p>In this example, <code>await</code> is used to ensure that both subtests have completed. This is necessary because parent tests do not wait for their subtests to complete. Any subtests that are still outstanding when their parent finishes are cancelled and treated as failures. Any subtest failures cause the parent test to fail.</p> </section><section><h3>Skipping tests<span><a class="mark" href="#skipping-tests" id="skipping-tests">#</a></span><a aria-hidden="true" class="legacy" id="test_skipping_tests"></a></h3> <p>Individual tests can be skipped by passing the <code>skip</code> option to the test, or by calling the test context's <code>skip()</code> method. Both of these options support including a message that is displayed in the TAP output as shown in the following example.</p> <pre><code class="language-js"><span class="hljs-comment">// The skip option is used, but no message is provided.</span> <span class="hljs-title function_">test</span>(<span class="hljs-string">'skip option'</span>, { <span class="hljs-attr">skip</span>: <span class="hljs-literal">true</span> }, <span class="hljs-function">(<span class="hljs-params">t</span>) =></span> { <span class="hljs-comment">// This code is never executed.</span> }); <span class="hljs-comment">// The skip option is used, and a message is provided.</span> <span class="hljs-title function_">test</span>(<span class="hljs-string">'skip option with message'</span>, { <span class="hljs-attr">skip</span>: <span class="hljs-string">'this is skipped'</span> }, <span class="hljs-function">(<span class="hljs-params">t</span>) =></span> { <span class="hljs-comment">// This code is never executed.</span> }); <span class="hljs-title function_">test</span>(<span class="hljs-string">'skip() method'</span>, <span class="hljs-function">(<span class="hljs-params">t</span>) =></span> { <span class="hljs-comment">// Make sure to return here as well if the test contains additional logic.</span> t.<span class="hljs-title function_">skip</span>(); }); <span class="hljs-title function_">test</span>(<span class="hljs-string">'skip() method with message'</span>, <span class="hljs-function">(<span class="hljs-params">t</span>) =></span> { <span class="hljs-comment">// Make sure to return here as well if the test contains additional logic.</span> t.<span class="hljs-title function_">skip</span>(<span class="hljs-string">'this is skipped'</span>); });</code></pre> </section><section><h3><code>describe</code>/<code>it</code> syntax<span><a class="mark" href="#describeit-syntax" id="describeit-syntax">#</a></span><a aria-hidden="true" class="legacy" id="test_describe_it_syntax"></a></h3> <p>Running tests can also be done using <code>describe</code> to declare a suite and <code>it</code> to declare a test. A suite is used to organize and group related tests together. <code>it</code> is an alias for <code>test</code>, except there is no test context passed, since nesting is done using suites.</p> <pre><code class="language-js"><span class="hljs-title function_">describe</span>(<span class="hljs-string">'A thing'</span>, <span class="hljs-function">() =></span> { <span class="hljs-title function_">it</span>(<span class="hljs-string">'should work'</span>, <span class="hljs-function">() =></span> { assert.<span class="hljs-title function_">strictEqual</span>(<span class="hljs-number">1</span>, <span class="hljs-number">1</span>); }); <span class="hljs-title function_">it</span>(<span class="hljs-string">'should be ok'</span>, <span class="hljs-function">() =></span> { assert.<span class="hljs-title function_">strictEqual</span>(<span class="hljs-number">2</span>, <span class="hljs-number">2</span>); }); <span class="hljs-title function_">describe</span>(<span class="hljs-string">'a nested thing'</span>, <span class="hljs-function">() =></span> { <span class="hljs-title function_">it</span>(<span class="hljs-string">'should work'</span>, <span class="hljs-function">() =></span> { assert.<span class="hljs-title function_">strictEqual</span>(<span class="hljs-number">3</span>, <span class="hljs-number">3</span>); }); }); });</code></pre> <p><code>describe</code> and <code>it</code> are imported from the <code>node:test</code> module.</p> <pre class="with-46-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> { describe, it } <span class="hljs-keyword">from</span> <span class="hljs-string">'node:test'</span>;</code><code class="language-js cjs"><span class="hljs-keyword">const</span> { describe, it } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:test'</span>);</code></pre> <h4><code>only</code> tests<span><a class="mark" href="#only-tests" id="only-tests">#</a></span><a aria-hidden="true" class="legacy" id="test_only_tests"></a></h4> <p>If Node.js is started with the <a href="cli.html#--test-only"><code>--test-only</code></a> command-line option, it is possible to skip all top level tests except for a selected subset by passing the <code>only</code> option to the tests that should be run. When a test with the <code>only</code> option set is run, all subtests are also run. The test context's <code>runOnly()</code> method can be used to implement the same behavior at the subtest level.</p> <pre><code class="language-js"><span class="hljs-comment">// Assume Node.js is run with the --test-only command-line option.</span> <span class="hljs-comment">// The 'only' option is set, so this test is run.</span> <span class="hljs-title function_">test</span>(<span class="hljs-string">'this test is run'</span>, { <span class="hljs-attr">only</span>: <span class="hljs-literal">true</span> }, <span class="hljs-keyword">async</span> (t) => { <span class="hljs-comment">// Within this test, all subtests are run by default.</span> <span class="hljs-keyword">await</span> t.<span class="hljs-title function_">test</span>(<span class="hljs-string">'running subtest'</span>); <span class="hljs-comment">// The test context can be updated to run subtests with the 'only' option.</span> t.<span class="hljs-title function_">runOnly</span>(<span class="hljs-literal">true</span>); <span class="hljs-keyword">await</span> t.<span class="hljs-title function_">test</span>(<span class="hljs-string">'this subtest is now skipped'</span>); <span class="hljs-keyword">await</span> t.<span class="hljs-title function_">test</span>(<span class="hljs-string">'this subtest is run'</span>, { <span class="hljs-attr">only</span>: <span class="hljs-literal">true</span> }); <span class="hljs-comment">// Switch the context back to execute all tests.</span> t.<span class="hljs-title function_">runOnly</span>(<span class="hljs-literal">false</span>); <span class="hljs-keyword">await</span> t.<span class="hljs-title function_">test</span>(<span class="hljs-string">'this subtest is now run'</span>); <span class="hljs-comment">// Explicitly do not run these tests.</span> <span class="hljs-keyword">await</span> t.<span class="hljs-title function_">test</span>(<span class="hljs-string">'skipped subtest 3'</span>, { <span class="hljs-attr">only</span>: <span class="hljs-literal">false</span> }); <span class="hljs-keyword">await</span> t.<span class="hljs-title function_">test</span>(<span class="hljs-string">'skipped subtest 4'</span>, { <span class="hljs-attr">skip</span>: <span class="hljs-literal">true</span> }); }); <span class="hljs-comment">// The 'only' option is not set, so this test is skipped.</span> <span class="hljs-title function_">test</span>(<span class="hljs-string">'this test is not run'</span>, <span class="hljs-function">() =></span> { <span class="hljs-comment">// This code is not run.</span> <span class="hljs-keyword">throw</span> <span class="hljs-keyword">new</span> <span class="hljs-title class_">Error</span>(<span class="hljs-string">'fail'</span>); });</code></pre> </section><section><h3>Extraneous asynchronous activity<span><a class="mark" href="#extraneous-asynchronous-activity" id="extraneous-asynchronous-activity">#</a></span><a aria-hidden="true" class="legacy" id="test_extraneous_asynchronous_activity"></a></h3> <p>Once a test function finishes executing, the TAP results are output as quickly as possible while maintaining the order of the tests. However, it is possible for the test function to generate asynchronous activity that outlives the test itself. The test runner handles this type of activity, but does not delay the reporting of test results in order to accommodate it.</p> <p>In the following example, a test completes with two <code>setImmediate()</code> operations still outstanding. The first <code>setImmediate()</code> attempts to create a new subtest. Because the parent test has already finished and output its results, the new subtest is immediately marked as failed, and reported in the top level of the file's TAP output.</p> <p>The second <code>setImmediate()</code> creates an <code>uncaughtException</code> event. <code>uncaughtException</code> and <code>unhandledRejection</code> events originating from a completed test are handled by the <code>test</code> module and reported as diagnostic warnings in the top level of the file's TAP output.</p> <pre><code class="language-js"><span class="hljs-title function_">test</span>(<span class="hljs-string">'a test that creates asynchronous activity'</span>, <span class="hljs-function">(<span class="hljs-params">t</span>) =></span> { <span class="hljs-title function_">setImmediate</span>(<span class="hljs-function">() =></span> { t.<span class="hljs-title function_">test</span>(<span class="hljs-string">'subtest that is created too late'</span>, <span class="hljs-function">(<span class="hljs-params">t</span>) =></span> { <span class="hljs-keyword">throw</span> <span class="hljs-keyword">new</span> <span class="hljs-title class_">Error</span>(<span class="hljs-string">'error1'</span>); }); }); <span class="hljs-title function_">setImmediate</span>(<span class="hljs-function">() =></span> { <span class="hljs-keyword">throw</span> <span class="hljs-keyword">new</span> <span class="hljs-title class_">Error</span>(<span class="hljs-string">'error2'</span>); }); <span class="hljs-comment">// The test finishes after this line.</span> });</code></pre> </section><section><h3>Running tests from the command line<span><a class="mark" href="#running-tests-from-the-command-line" id="running-tests-from-the-command-line">#</a></span><a aria-hidden="true" class="legacy" id="test_running_tests_from_the_command_line"></a></h3> <p>The Node.js test runner can be invoked from the command line by passing the <a href="cli.html#--test"><code>--test</code></a> flag:</p> <pre><code class="language-bash">node --<span class="hljs-built_in">test</span></code></pre> <p>By default, Node.js will recursively search the current directory for JavaScript source files matching a specific naming convention. Matching files are executed as test files. More information on the expected test file naming convention and behavior can be found in the <a href="#test-runner-execution-model">test runner execution model</a> section.</p> <p>Alternatively, one or more paths can be provided as the final argument(s) to the Node.js command, as shown below.</p> <pre><code class="language-bash">node --<span class="hljs-built_in">test</span> test1.js test2.mjs custom_test_dir/</code></pre> <p>In this example, the test runner will execute the files <code>test1.js</code> and <code>test2.mjs</code>. The test runner will also recursively search the <code>custom_test_dir/</code> directory for test files to execute.</p> <h4>Test runner execution model<span><a class="mark" href="#test-runner-execution-model" id="test-runner-execution-model">#</a></span><a aria-hidden="true" class="legacy" id="test_test_runner_execution_model"></a></h4> <p>When searching for test files to execute, the test runner behaves as follows:</p> <ul> <li>Any files explicitly provided by the user are executed.</li> <li>If the user did not explicitly specify any paths, the current working directory is recursively searched for files as specified in the following steps.</li> <li><code>node_modules</code> directories are skipped unless explicitly provided by the user.</li> <li>If a directory named <code>test</code> is encountered, the test runner will search it recursively for all all <code>.js</code>, <code>.cjs</code>, and <code>.mjs</code> files. All of these files are treated as test files, and do not need to match the specific naming convention detailed below. This is to accommodate projects that place all of their tests in a single <code>test</code> directory.</li> <li>In all other directories, <code>.js</code>, <code>.cjs</code>, and <code>.mjs</code> files matching the following patterns are treated as test files: <ul> <li><code>^test$</code> - Files whose basename is the string <code>'test'</code>. Examples: <code>test.js</code>, <code>test.cjs</code>, <code>test.mjs</code>.</li> <li><code>^test-.+</code> - Files whose basename starts with the string <code>'test-'</code> followed by one or more characters. Examples: <code>test-example.js</code>, <code>test-another-example.mjs</code>.</li> <li><code>.+[\.\-\_]test$</code> - Files whose basename ends with <code>.test</code>, <code>-test</code>, or <code>_test</code>, preceded by one or more characters. Examples: <code>example.test.js</code>, <code>example-test.cjs</code>, <code>example_test.mjs</code>.</li> <li>Other file types understood by Node.js such as <code>.node</code> and <code>.json</code> are not automatically executed by the test runner, but are supported if explicitly provided on the command line.</li> </ul> </li> </ul> <p>Each matching test file is executed in a separate child process. If the child process finishes with an exit code of 0, the test is considered passing. Otherwise, the test is considered to be a failure. Test files must be executable by Node.js, but are not required to use the <code>node:test</code> module internally.</p> </section><section><h3><code>run([options])</code><span><a class="mark" href="#runoptions" id="runoptions">#</a></span><a aria-hidden="true" class="legacy" id="test_run_options"></a></h3> <div class="api_metadata"> <span>Added in: v16.19.0</span> </div> <ul> <li><code>options</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> Configuration options for running tests. The following properties are supported: <ul> <li><code>concurrency</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> If a number is provided, then that many files would run in parallel. If truthy, it would run (number of cpu cores - 1) files in parallel. If falsy, it would only run one file at a time. If unspecified, subtests inherit this value from their parent. <strong>Default:</strong> <code>true</code>.</li> <li><code>files</code>: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array" class="type"><Array></a> An array containing the list of files to run. <strong>Default</strong> matching files from <a href="#test-runner-execution-model">test runner execution model</a>.</li> <li><code>signal</code> <a href="globals.html#class-abortsignal" class="type"><AbortSignal></a> Allows aborting an in-progress test execution.</li> <li><code>timeout</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> A number of milliseconds the test execution will fail after. If unspecified, subtests inherit this value from their parent. <strong>Default:</strong> <code>Infinity</code>.</li> <li><code>inspectPort</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> Sets inspector port of test child process. This can be a number, or a function that takes no arguments and returns a number. If a nullish value is provided, each process gets its own port, incremented from the primary's <code>process.debugPort</code>. <strong>Default:</strong> <code>undefined</code>.</li> </ul> </li> <li>Returns: <a href="test.html#class-tapstream" class="type"><TapStream></a></li> </ul> <pre><code class="language-js"><span class="hljs-title function_">run</span>({ <span class="hljs-attr">files</span>: [path.<span class="hljs-title function_">resolve</span>(<span class="hljs-string">'./tests/test.js'</span>)] }) .<span class="hljs-title function_">pipe</span>(process.<span class="hljs-property">stdout</span>);</code></pre> </section><section><h3><code>test([name][, options][, fn])</code><span><a class="mark" href="#testname-options-fn" id="testname-options-fn">#</a></span><a aria-hidden="true" class="legacy" id="test_test_name_options_fn"></a></h3> <div class="api_metadata"> <details class="changelog"><summary>History</summary> <table> <tbody><tr><th>Version</th><th>Changes</th></tr> <tr><td>v16.18.0</td> <td><p>Add a <code>signal</code> option.</p></td></tr> <tr><td>v16.17.0</td> <td><p>Add a <code>timeout</code> option.</p></td></tr> <tr><td>v16.17.0</td> <td><p><span>Added in: v16.17.0</span></p></td></tr> </tbody></table> </details> </div> <ul> <li><code>name</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> The name of the test, which is displayed when reporting test results. <strong>Default:</strong> The <code>name</code> property of <code>fn</code>, or <code>'<anonymous>'</code> if <code>fn</code> does not have a name.</li> <li><code>options</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> Configuration options for the test. The following properties are supported: <ul> <li><code>concurrency</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> If a number is provided, then that many tests would run in parallel. If truthy, it would run (number of cpu cores - 1) tests in parallel. For subtests, it will be <code>Infinity</code> tests in parallel. If falsy, it would only run one test at a time. If unspecified, subtests inherit this value from their parent. <strong>Default:</strong> <code>false</code>.</li> <li><code>only</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> If truthy, and the test context is configured to run <code>only</code> tests, then this test will be run. Otherwise, the test is skipped. <strong>Default:</strong> <code>false</code>.</li> <li><code>signal</code> <a href="globals.html#class-abortsignal" class="type"><AbortSignal></a> Allows aborting an in-progress test.</li> <li><code>skip</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> If truthy, the test is skipped. If a string is provided, that string is displayed in the test results as the reason for skipping the test. <strong>Default:</strong> <code>false</code>.</li> <li><code>todo</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> If truthy, the test marked as <code>TODO</code>. If a string is provided, that string is displayed in the test results as the reason why the test is <code>TODO</code>. <strong>Default:</strong> <code>false</code>.</li> <li><code>timeout</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> A number of milliseconds the test will fail after. If unspecified, subtests inherit this value from their parent. <strong>Default:</strong> <code>Infinity</code>.</li> </ul> </li> <li><code>fn</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> | <a href="https://tc39.es/ecma262/#sec-async-function-constructor" class="type"><AsyncFunction></a> The function under test. The first argument to this function is a <a href="#class-testcontext"><code>TestContext</code></a> object. If the test uses callbacks, the callback function is passed as the second argument. <strong>Default:</strong> A no-op function.</li> <li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise" class="type"><Promise></a> Resolved with <code>undefined</code> once the test completes.</li> </ul> <p>The <code>test()</code> function is the value imported from the <code>test</code> module. Each invocation of this function results in the creation of a test point in the TAP output.</p> <p>The <code>TestContext</code> object passed to the <code>fn</code> argument can be used to perform actions related to the current test. Examples include skipping the test, adding additional TAP diagnostic information, or creating subtests.</p> <p><code>test()</code> returns a <code>Promise</code> that resolves once the test completes. The return value can usually be discarded for top level tests. However, the return value from subtests should be used to prevent the parent test from finishing first and cancelling the subtest as shown in the following example.</p> <pre><code class="language-js"><span class="hljs-title function_">test</span>(<span class="hljs-string">'top level test'</span>, <span class="hljs-keyword">async</span> (t) => { <span class="hljs-comment">// The setTimeout() in the following subtest would cause it to outlive its</span> <span class="hljs-comment">// parent test if 'await' is removed on the next line. Once the parent test</span> <span class="hljs-comment">// completes, it will cancel any outstanding subtests.</span> <span class="hljs-keyword">await</span> t.<span class="hljs-title function_">test</span>(<span class="hljs-string">'longer running subtest'</span>, <span class="hljs-keyword">async</span> (t) => { <span class="hljs-keyword">return</span> <span class="hljs-keyword">new</span> <span class="hljs-title class_">Promise</span>(<span class="hljs-function">(<span class="hljs-params">resolve, reject</span>) =></span> { <span class="hljs-built_in">setTimeout</span>(resolve, <span class="hljs-number">1000</span>); }); }); });</code></pre> <p>The <code>timeout</code> option can be used to fail the test if it takes longer than <code>timeout</code> milliseconds to complete. However, it is not a reliable mechanism for canceling tests because a running test might block the application thread and thus prevent the scheduled cancellation.</p> </section><section><h3><code>describe([name][, options][, fn])</code><span><a class="mark" href="#describename-options-fn" id="describename-options-fn">#</a></span><a aria-hidden="true" class="legacy" id="test_describe_name_options_fn"></a></h3> <ul> <li><code>name</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> The name of the suite, which is displayed when reporting test results. <strong>Default:</strong> The <code>name</code> property of <code>fn</code>, or <code>'<anonymous>'</code> if <code>fn</code> does not have a name.</li> <li><code>options</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> Configuration options for the suite. supports the same options as <code>test([name][, options][, fn])</code>.</li> <li><code>fn</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> | <a href="https://tc39.es/ecma262/#sec-async-function-constructor" class="type"><AsyncFunction></a> The function under suite declaring all subtests and subsuites. The first argument to this function is a <a href="#class-suitecontext"><code>SuiteContext</code></a> object. <strong>Default:</strong> A no-op function.</li> <li>Returns: <code>undefined</code>.</li> </ul> <p>The <code>describe()</code> function imported from the <code>node:test</code> module. Each invocation of this function results in the creation of a Subtest and a test point in the TAP output. After invocation of top level <code>describe</code> functions, all top level tests and suites will execute.</p> </section><section><h3><code>describe.skip([name][, options][, fn])</code><span><a class="mark" href="#describeskipname-options-fn" id="describeskipname-options-fn">#</a></span><a aria-hidden="true" class="legacy" id="test_describe_skip_name_options_fn"></a></h3> <p>Shorthand for skipping a suite, same as <a href="#describename-options-fn"><code>describe([name], { skip: true }[, fn])</code></a>.</p> </section><section><h3><code>describe.todo([name][, options][, fn])</code><span><a class="mark" href="#describetodoname-options-fn" id="describetodoname-options-fn">#</a></span><a aria-hidden="true" class="legacy" id="test_describe_todo_name_options_fn"></a></h3> <p>Shorthand for marking a suite as <code>TODO</code>, same as <a href="#describename-options-fn"><code>describe([name], { todo: true }[, fn])</code></a>.</p> </section><section><h3><code>it([name][, options][, fn])</code><span><a class="mark" href="#itname-options-fn" id="itname-options-fn">#</a></span><a aria-hidden="true" class="legacy" id="test_it_name_options_fn"></a></h3> <ul> <li><code>name</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> The name of the test, which is displayed when reporting test results. <strong>Default:</strong> The <code>name</code> property of <code>fn</code>, or <code>'<anonymous>'</code> if <code>fn</code> does not have a name.</li> <li><code>options</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> Configuration options for the suite. supports the same options as <code>test([name][, options][, fn])</code>.</li> <li><code>fn</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> | <a href="https://tc39.es/ecma262/#sec-async-function-constructor" class="type"><AsyncFunction></a> The function under test. If the test uses callbacks, the callback function is passed as an argument. <strong>Default:</strong> A no-op function.</li> <li>Returns: <code>undefined</code>.</li> </ul> <p>The <code>it()</code> function is the value imported from the <code>node:test</code> module. Each invocation of this function results in the creation of a test point in the TAP output.</p> </section><section><h3><code>it.skip([name][, options][, fn])</code><span><a class="mark" href="#itskipname-options-fn" id="itskipname-options-fn">#</a></span><a aria-hidden="true" class="legacy" id="test_it_skip_name_options_fn"></a></h3> <p>Shorthand for skipping a test, same as <a href="#testname-options-fn"><code>it([name], { skip: true }[, fn])</code></a>.</p> </section><section><h3><code>it.todo([name][, options][, fn])</code><span><a class="mark" href="#ittodoname-options-fn" id="ittodoname-options-fn">#</a></span><a aria-hidden="true" class="legacy" id="test_it_todo_name_options_fn"></a></h3> <p>Shorthand for marking a test as <code>TODO</code>, same as <a href="#testname-options-fn"><code>it([name], { todo: true }[, fn])</code></a>.</p> </section><section><h3><code>before([, fn][, options])</code><span><a class="mark" href="#before-fn-options" id="before-fn-options">#</a></span><a aria-hidden="true" class="legacy" id="test_before_fn_options"></a></h3> <div class="api_metadata"> <span>Added in: v16.18.0</span> </div> <ul> <li><code>fn</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> | <a href="https://tc39.es/ecma262/#sec-async-function-constructor" class="type"><AsyncFunction></a> The hook function. If the hook uses callbacks, the callback function is passed as the second argument. <strong>Default:</strong> A no-op function.</li> <li><code>options</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> Configuration options for the hook. The following properties are supported: <ul> <li><code>signal</code> <a href="globals.html#class-abortsignal" class="type"><AbortSignal></a> Allows aborting an in-progress hook.</li> <li><code>timeout</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> A number of milliseconds the hook will fail after. If unspecified, subtests inherit this value from their parent. <strong>Default:</strong> <code>Infinity</code>.</li> </ul> </li> </ul> <p>This function is used to create a hook running before running a suite.</p> <pre><code class="language-js"><span class="hljs-title function_">describe</span>(<span class="hljs-string">'tests'</span>, <span class="hljs-keyword">async</span> () => { <span class="hljs-title function_">before</span>(<span class="hljs-function">() =></span> <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">'about to run some test'</span>)); <span class="hljs-title function_">it</span>(<span class="hljs-string">'is a subtest'</span>, <span class="hljs-function">() =></span> { assert.<span class="hljs-title function_">ok</span>(<span class="hljs-string">'some relevant assertion here'</span>); }); });</code></pre> </section><section><h3><code>after([, fn][, options])</code><span><a class="mark" href="#after-fn-options" id="after-fn-options">#</a></span><a aria-hidden="true" class="legacy" id="test_after_fn_options"></a></h3> <div class="api_metadata"> <span>Added in: v16.18.0</span> </div> <ul> <li><code>fn</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> | <a href="https://tc39.es/ecma262/#sec-async-function-constructor" class="type"><AsyncFunction></a> The hook function. If the hook uses callbacks, the callback function is passed as the second argument. <strong>Default:</strong> A no-op function.</li> <li><code>options</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> Configuration options for the hook. The following properties are supported: <ul> <li><code>signal</code> <a href="globals.html#class-abortsignal" class="type"><AbortSignal></a> Allows aborting an in-progress hook.</li> <li><code>timeout</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> A number of milliseconds the hook will fail after. If unspecified, subtests inherit this value from their parent. <strong>Default:</strong> <code>Infinity</code>.</li> </ul> </li> </ul> <p>This function is used to create a hook running after running a suite.</p> <pre><code class="language-js"><span class="hljs-title function_">describe</span>(<span class="hljs-string">'tests'</span>, <span class="hljs-keyword">async</span> () => { <span class="hljs-title function_">after</span>(<span class="hljs-function">() =></span> <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">'finished running tests'</span>)); <span class="hljs-title function_">it</span>(<span class="hljs-string">'is a subtest'</span>, <span class="hljs-function">() =></span> { assert.<span class="hljs-title function_">ok</span>(<span class="hljs-string">'some relevant assertion here'</span>); }); });</code></pre> </section><section><h3><code>beforeEach([, fn][, options])</code><span><a class="mark" href="#beforeeach-fn-options" id="beforeeach-fn-options">#</a></span><a aria-hidden="true" class="legacy" id="test_beforeeach_fn_options"></a></h3> <div class="api_metadata"> <span>Added in: v16.18.0</span> </div> <ul> <li><code>fn</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> | <a href="https://tc39.es/ecma262/#sec-async-function-constructor" class="type"><AsyncFunction></a> The hook function. If the hook uses callbacks, the callback function is passed as the second argument. <strong>Default:</strong> A no-op function.</li> <li><code>options</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> Configuration options for the hook. The following properties are supported: <ul> <li><code>signal</code> <a href="globals.html#class-abortsignal" class="type"><AbortSignal></a> Allows aborting an in-progress hook.</li> <li><code>timeout</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> A number of milliseconds the hook will fail after. If unspecified, subtests inherit this value from their parent. <strong>Default:</strong> <code>Infinity</code>.</li> </ul> </li> </ul> <p>This function is used to create a hook running before each subtest of the current suite.</p> <pre><code class="language-js"><span class="hljs-title function_">describe</span>(<span class="hljs-string">'tests'</span>, <span class="hljs-keyword">async</span> () => { <span class="hljs-title function_">beforeEach</span>(<span class="hljs-function">() =></span> t.<span class="hljs-title function_">diagnostic</span>(<span class="hljs-string">'about to run a test'</span>)); <span class="hljs-title function_">it</span>(<span class="hljs-string">'is a subtest'</span>, <span class="hljs-function">() =></span> { assert.<span class="hljs-title function_">ok</span>(<span class="hljs-string">'some relevant assertion here'</span>); }); });</code></pre> </section><section><h3><code>afterEach([, fn][, options])</code><span><a class="mark" href="#aftereach-fn-options" id="aftereach-fn-options">#</a></span><a aria-hidden="true" class="legacy" id="test_aftereach_fn_options"></a></h3> <div class="api_metadata"> <span>Added in: v16.18.0</span> </div> <ul> <li><code>fn</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> | <a href="https://tc39.es/ecma262/#sec-async-function-constructor" class="type"><AsyncFunction></a> The hook function. If the hook uses callbacks, the callback function is passed as the second argument. <strong>Default:</strong> A no-op function.</li> <li><code>options</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> Configuration options for the hook. The following properties are supported: <ul> <li><code>signal</code> <a href="globals.html#class-abortsignal" class="type"><AbortSignal></a> Allows aborting an in-progress hook.</li> <li><code>timeout</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> A number of milliseconds the hook will fail after. If unspecified, subtests inherit this value from their parent. <strong>Default:</strong> <code>Infinity</code>.</li> </ul> </li> </ul> <p>This function is used to create a hook running after each subtest of the current test.</p> <pre><code class="language-js"><span class="hljs-title function_">describe</span>(<span class="hljs-string">'tests'</span>, <span class="hljs-keyword">async</span> () => { <span class="hljs-title function_">afterEach</span>(<span class="hljs-function">() =></span> t.<span class="hljs-title function_">diagnostic</span>(<span class="hljs-string">'about to run a test'</span>)); <span class="hljs-title function_">it</span>(<span class="hljs-string">'is a subtest'</span>, <span class="hljs-function">() =></span> { assert.<span class="hljs-title function_">ok</span>(<span class="hljs-string">'some relevant assertion here'</span>); }); });</code></pre> </section><section><h3>Class: <code>TapStream</code><span><a class="mark" href="#class-tapstream" id="class-tapstream">#</a></span><a aria-hidden="true" class="legacy" id="test_class_tapstream"></a></h3> <div class="api_metadata"> <span>Added in: v16.19.0</span> </div> <ul> <li>Extends <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a></li> </ul> <p>A successful call to <a href="#runoptions"><code>run()</code></a> method will return a new <a href="test.html#class-tapstream" class="type"><TapStream></a> object, streaming a <a href="https://testanything.org/">TAP</a> output <code>TapStream</code> will emit events, in the order of the tests definition</p> <h4>Event: <code>'test:diagnostic'</code><span><a class="mark" href="#event-testdiagnostic" id="event-testdiagnostic">#</a></span><a aria-hidden="true" class="legacy" id="test_event_test_diagnostic"></a></h4> <ul> <li><code>message</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> The diagnostic message.</li> </ul> <p>Emitted when <a href="#contextdiagnosticmessage"><code>context.diagnostic</code></a> is called.</p> <h4>Event: <code>'test:fail'</code><span><a class="mark" href="#event-testfail" id="event-testfail">#</a></span><a aria-hidden="true" class="legacy" id="test_event_test_fail"></a></h4> <ul> <li><code>data</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> <ul> <li><code>duration</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> The test duration.</li> <li><code>error</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error" class="type"><Error></a> The failure casing test to fail.</li> <li><code>name</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> The test name.</li> <li><code>testNumber</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> The ordinal number of the test.</li> <li><code>todo</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/Data_structures#Undefined_type" class="type"><undefined></a> Present if <a href="#contexttodomessage"><code>context.todo</code></a> is called</li> <li><code>skip</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/Data_structures#Undefined_type" class="type"><undefined></a> Present if <a href="#contextskipmessage"><code>context.skip</code></a> is called</li> </ul> </li> </ul> <p>Emitted when a test fails.</p> <h4>Event: <code>'test:pass'</code><span><a class="mark" href="#event-testpass" id="event-testpass">#</a></span><a aria-hidden="true" class="legacy" id="test_event_test_pass"></a></h4> <ul> <li><code>data</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> <ul> <li><code>duration</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> The test duration.</li> <li><code>name</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> The test name.</li> <li><code>testNumber</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> The ordinal number of the test.</li> <li><code>todo</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/Data_structures#Undefined_type" class="type"><undefined></a> Present if <a href="#contexttodomessage"><code>context.todo</code></a> is called</li> <li><code>skip</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/Data_structures#Undefined_type" class="type"><undefined></a> Present if <a href="#contextskipmessage"><code>context.skip</code></a> is called</li> </ul> </li> </ul> <p>Emitted when a test passes.</p> </section><section><h3>Class: <code>TestContext</code><span><a class="mark" href="#class-testcontext" id="class-testcontext">#</a></span><a aria-hidden="true" class="legacy" id="test_class_testcontext"></a></h3> <div class="api_metadata"> <span>Added in: v16.17.0</span> </div> <p>An instance of <code>TestContext</code> is passed to each test function in order to interact with the test runner. However, the <code>TestContext</code> constructor is not exposed as part of the API.</p> <h4><code>context.beforeEach([, fn][, options])</code><span><a class="mark" href="#contextbeforeeach-fn-options" id="contextbeforeeach-fn-options">#</a></span><a aria-hidden="true" class="legacy" id="test_context_beforeeach_fn_options"></a></h4> <div class="api_metadata"> <span>Added in: v16.18.0</span> </div> <ul> <li><code>fn</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> | <a href="https://tc39.es/ecma262/#sec-async-function-constructor" class="type"><AsyncFunction></a> The hook function. The first argument to this function is a <a href="#class-testcontext"><code>TestContext</code></a> object. If the hook uses callbacks, the callback function is passed as the second argument. <strong>Default:</strong> A no-op function.</li> <li><code>options</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> Configuration options for the hook. The following properties are supported: <ul> <li><code>signal</code> <a href="globals.html#class-abortsignal" class="type"><AbortSignal></a> Allows aborting an in-progress hook.</li> <li><code>timeout</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> A number of milliseconds the hook will fail after. If unspecified, subtests inherit this value from their parent. <strong>Default:</strong> <code>Infinity</code>.</li> </ul> </li> </ul> <p>This function is used to create a hook running before each subtest of the current test.</p> <pre><code class="language-js"><span class="hljs-title function_">test</span>(<span class="hljs-string">'top level test'</span>, <span class="hljs-keyword">async</span> (t) => { t.<span class="hljs-title function_">beforeEach</span>(<span class="hljs-function">(<span class="hljs-params">t</span>) =></span> t.<span class="hljs-title function_">diagnostic</span>(<span class="hljs-string">`about to run <span class="hljs-subst">${t.name}</span>`</span>)); <span class="hljs-keyword">await</span> t.<span class="hljs-title function_">test</span>( <span class="hljs-string">'This is a subtest'</span>, <span class="hljs-function">(<span class="hljs-params">t</span>) =></span> { assert.<span class="hljs-title function_">ok</span>(<span class="hljs-string">'some relevant assertion here'</span>); } ); });</code></pre> <h4><code>context.afterEach([, fn][, options])</code><span><a class="mark" href="#contextaftereach-fn-options" id="contextaftereach-fn-options">#</a></span><a aria-hidden="true" class="legacy" id="test_context_aftereach_fn_options"></a></h4> <div class="api_metadata"> <span>Added in: v16.18.0</span> </div> <ul> <li><code>fn</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> | <a href="https://tc39.es/ecma262/#sec-async-function-constructor" class="type"><AsyncFunction></a> The hook function. The first argument to this function is a <a href="#class-testcontext"><code>TestContext</code></a> object. If the hook uses callbacks, the callback function is passed as the second argument. <strong>Default:</strong> A no-op function.</li> <li><code>options</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> Configuration options for the hook. The following properties are supported: <ul> <li><code>signal</code> <a href="globals.html#class-abortsignal" class="type"><AbortSignal></a> Allows aborting an in-progress hook.</li> <li><code>timeout</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> A number of milliseconds the hook will fail after. If unspecified, subtests inherit this value from their parent. <strong>Default:</strong> <code>Infinity</code>.</li> </ul> </li> </ul> <p>This function is used to create a hook running after each subtest of the current test.</p> <pre><code class="language-js"><span class="hljs-title function_">test</span>(<span class="hljs-string">'top level test'</span>, <span class="hljs-keyword">async</span> (t) => { t.<span class="hljs-title function_">afterEach</span>(<span class="hljs-function">(<span class="hljs-params">t</span>) =></span> t.<span class="hljs-title function_">diagnostic</span>(<span class="hljs-string">`finished running <span class="hljs-subst">${t.name}</span>`</span>)); <span class="hljs-keyword">await</span> t.<span class="hljs-title function_">test</span>( <span class="hljs-string">'This is a subtest'</span>, <span class="hljs-function">(<span class="hljs-params">t</span>) =></span> { assert.<span class="hljs-title function_">ok</span>(<span class="hljs-string">'some relevant assertion here'</span>); } ); });</code></pre> <h4><code>context.diagnostic(message)</code><span><a class="mark" href="#contextdiagnosticmessage" id="contextdiagnosticmessage">#</a></span><a aria-hidden="true" class="legacy" id="test_context_diagnostic_message"></a></h4> <div class="api_metadata"> <span>Added in: v16.17.0</span> </div> <ul> <li><code>message</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> Message to be displayed as a TAP diagnostic.</li> </ul> <p>This function is used to write TAP diagnostics to the output. Any diagnostic information is included at the end of the test's results. This function does not return a value.</p> <pre><code class="language-js"><span class="hljs-title function_">test</span>(<span class="hljs-string">'top level test'</span>, <span class="hljs-function">(<span class="hljs-params">t</span>) =></span> { t.<span class="hljs-title function_">diagnostic</span>(<span class="hljs-string">'A diagnostic message'</span>); });</code></pre> <h4><code>context.name</code><span><a class="mark" href="#contextname" id="contextname">#</a></span><a aria-hidden="true" class="legacy" id="test_context_name"></a></h4> <div class="api_metadata"> <span>Added in: v16.18.0</span> </div> <p>The name of the test.</p> <h4><code>context.runOnly(shouldRunOnlyTests)</code><span><a class="mark" href="#contextrunonlyshouldrunonlytests" id="contextrunonlyshouldrunonlytests">#</a></span><a aria-hidden="true" class="legacy" id="test_context_runonly_shouldrunonlytests"></a></h4> <div class="api_metadata"> <span>Added in: v16.17.0</span> </div> <ul> <li><code>shouldRunOnlyTests</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> Whether or not to run <code>only</code> tests.</li> </ul> <p>If <code>shouldRunOnlyTests</code> is truthy, the test context will only run tests that have the <code>only</code> option set. Otherwise, all tests are run. If Node.js was not started with the <a href="cli.html#--test-only"><code>--test-only</code></a> command-line option, this function is a no-op.</p> <pre><code class="language-js"><span class="hljs-title function_">test</span>(<span class="hljs-string">'top level test'</span>, <span class="hljs-function">(<span class="hljs-params">t</span>) =></span> { <span class="hljs-comment">// The test context can be set to run subtests with the 'only' option.</span> t.<span class="hljs-title function_">runOnly</span>(<span class="hljs-literal">true</span>); <span class="hljs-keyword">return</span> <span class="hljs-title class_">Promise</span>.<span class="hljs-title function_">all</span>([ t.<span class="hljs-title function_">test</span>(<span class="hljs-string">'this subtest is now skipped'</span>), t.<span class="hljs-title function_">test</span>(<span class="hljs-string">'this subtest is run'</span>, { <span class="hljs-attr">only</span>: <span class="hljs-literal">true</span> }), ]); });</code></pre> <h4><code>context.signal</code><span><a class="mark" href="#contextsignal" id="contextsignal">#</a></span><a aria-hidden="true" class="legacy" id="test_context_signal"></a></h4> <div class="api_metadata"> <span>Added in: v16.17.0</span> </div> <ul> <li><a href="globals.html#class-abortsignal" class="type"><AbortSignal></a> Can be used to abort test subtasks when the test has been aborted.</li> </ul> <pre><code class="language-js"><span class="hljs-title function_">test</span>(<span class="hljs-string">'top level test'</span>, <span class="hljs-keyword">async</span> (t) => { <span class="hljs-keyword">await</span> <span class="hljs-title function_">fetch</span>(<span class="hljs-string">'some/uri'</span>, { <span class="hljs-attr">signal</span>: t.<span class="hljs-property">signal</span> }); });</code></pre> <h4><code>context.skip([message])</code><span><a class="mark" href="#contextskipmessage" id="contextskipmessage">#</a></span><a aria-hidden="true" class="legacy" id="test_context_skip_message"></a></h4> <div class="api_metadata"> <span>Added in: v16.17.0</span> </div> <ul> <li><code>message</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> Optional skip message to be displayed in TAP output.</li> </ul> <p>This function causes the test's output to indicate the test as skipped. If <code>message</code> is provided, it is included in the TAP output. Calling <code>skip()</code> does not terminate execution of the test function. This function does not return a value.</p> <pre><code class="language-js"><span class="hljs-title function_">test</span>(<span class="hljs-string">'top level test'</span>, <span class="hljs-function">(<span class="hljs-params">t</span>) =></span> { <span class="hljs-comment">// Make sure to return here as well if the test contains additional logic.</span> t.<span class="hljs-title function_">skip</span>(<span class="hljs-string">'this is skipped'</span>); });</code></pre> <h4><code>context.todo([message])</code><span><a class="mark" href="#contexttodomessage" id="contexttodomessage">#</a></span><a aria-hidden="true" class="legacy" id="test_context_todo_message"></a></h4> <div class="api_metadata"> <span>Added in: v16.17.0</span> </div> <ul> <li><code>message</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> Optional <code>TODO</code> message to be displayed in TAP output.</li> </ul> <p>This function adds a <code>TODO</code> directive to the test's output. If <code>message</code> is provided, it is included in the TAP output. Calling <code>todo()</code> does not terminate execution of the test function. This function does not return a value.</p> <pre><code class="language-js"><span class="hljs-title function_">test</span>(<span class="hljs-string">'top level test'</span>, <span class="hljs-function">(<span class="hljs-params">t</span>) =></span> { <span class="hljs-comment">// This test is marked as `TODO`</span> t.<span class="hljs-title function_">todo</span>(<span class="hljs-string">'this is a todo'</span>); });</code></pre> <h4><code>context.test([name][, options][, fn])</code><span><a class="mark" href="#contexttestname-options-fn" id="contexttestname-options-fn">#</a></span><a aria-hidden="true" class="legacy" id="test_context_test_name_options_fn"></a></h4> <div class="api_metadata"> <details class="changelog"><summary>History</summary> <table> <tbody><tr><th>Version</th><th>Changes</th></tr> <tr><td>v16.18.0</td> <td><p>Add a <code>signal</code> option.</p></td></tr> <tr><td>v16.17.0</td> <td><p>Add a <code>timeout</code> option.</p></td></tr> <tr><td>v16.17.0</td> <td><p><span>Added in: v16.17.0</span></p></td></tr> </tbody></table> </details> </div> <ul> <li><code>name</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> The name of the subtest, which is displayed when reporting test results. <strong>Default:</strong> The <code>name</code> property of <code>fn</code>, or <code>'<anonymous>'</code> if <code>fn</code> does not have a name.</li> <li><code>options</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> Configuration options for the subtest. The following properties are supported: <ul> <li><code>concurrency</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> The number of tests that can be run at the same time. If unspecified, subtests inherit this value from their parent. <strong>Default:</strong> <code>1</code>.</li> <li><code>only</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> If truthy, and the test context is configured to run <code>only</code> tests, then this test will be run. Otherwise, the test is skipped. <strong>Default:</strong> <code>false</code>.</li> <li><code>signal</code> <a href="globals.html#class-abortsignal" class="type"><AbortSignal></a> Allows aborting an in-progress test.</li> <li><code>skip</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> If truthy, the test is skipped. If a string is provided, that string is displayed in the test results as the reason for skipping the test. <strong>Default:</strong> <code>false</code>.</li> <li><code>todo</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> If truthy, the test marked as <code>TODO</code>. If a string is provided, that string is displayed in the test results as the reason why the test is <code>TODO</code>. <strong>Default:</strong> <code>false</code>.</li> <li><code>timeout</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> A number of milliseconds the test will fail after. If unspecified, subtests inherit this value from their parent. <strong>Default:</strong> <code>Infinity</code>.</li> </ul> </li> <li><code>fn</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> | <a href="https://tc39.es/ecma262/#sec-async-function-constructor" class="type"><AsyncFunction></a> The function under test. The first argument to this function is a <a href="#class-testcontext"><code>TestContext</code></a> object. If the test uses callbacks, the callback function is passed as the second argument. <strong>Default:</strong> A no-op function.</li> <li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise" class="type"><Promise></a> Resolved with <code>undefined</code> once the test completes.</li> </ul> <p>This function is used to create subtests under the current test. This function behaves in the same fashion as the top level <a href="#testname-options-fn"><code>test()</code></a> function.</p> <pre><code class="language-js"><span class="hljs-title function_">test</span>(<span class="hljs-string">'top level test'</span>, <span class="hljs-keyword">async</span> (t) => { <span class="hljs-keyword">await</span> t.<span class="hljs-title function_">test</span>( <span class="hljs-string">'This is a subtest'</span>, { <span class="hljs-attr">only</span>: <span class="hljs-literal">false</span>, <span class="hljs-attr">skip</span>: <span class="hljs-literal">false</span>, <span class="hljs-attr">concurrency</span>: <span class="hljs-number">1</span>, <span class="hljs-attr">todo</span>: <span class="hljs-literal">false</span> }, <span class="hljs-function">(<span class="hljs-params">t</span>) =></span> { assert.<span class="hljs-title function_">ok</span>(<span class="hljs-string">'some relevant assertion here'</span>); } ); });</code></pre> </section><section><h3>Class: <code>SuiteContext</code><span><a class="mark" href="#class-suitecontext" id="class-suitecontext">#</a></span><a aria-hidden="true" class="legacy" id="test_class_suitecontext"></a></h3> <div class="api_metadata"> <span>Added in: v16.17.0</span> </div> <p>An instance of <code>SuiteContext</code> is passed to each suite function in order to interact with the test runner. However, the <code>SuiteContext</code> constructor is not exposed as part of the API.</p> <h4><code>context.name</code><span><a class="mark" href="#contextname_1" id="contextname_1">#</a></span><a aria-hidden="true" class="legacy" id="test_context_name_1"></a></h4> <div class="api_metadata"> <span>Added in: v16.18.0</span> </div> <p>The name of the suite.</p> <h4><code>context.signal</code><span><a class="mark" href="#contextsignal_1" id="contextsignal_1">#</a></span><a aria-hidden="true" class="legacy" id="test_context_signal_1"></a></h4> <div class="api_metadata"> <span>Added in: v16.17.0</span> </div> <ul> <li><a href="globals.html#class-abortsignal" class="type"><AbortSignal></a> Can be used to abort test subtasks when the test has been aborted.</li> </ul></section> <!-- API END --> </div> </div> </div> </body> </html>
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