test_runner: export describe and it

doc/api/test.md

@@ -148,6 +148,42 @@ test('skip() method with message', (t) => {
 });
 ```
 
+## `describe`/`it` syntax
+
+Running tests can also be done using `describe` to declare a suite
+and `it` to declare a test.
+A suite is used to organize and group related tests together.
+`it` is an alias for `test`, except there is no test context passed,
+since nesting is done using suites, as demonstrated in this example
+
+```js
+describe('A thing', () => {
+  it('should work', () => {
+    assert.strictEqual(1, 1);
+  });
+
+  it('should be ok', () => {
+    assert.strictEqual(2, 2);
+  });
+
+  describe('a nested thing', () => {
+    it('should work', () => {
+      assert.strictEqual(3, 3);
+    });
+  });
+});
+```
+
+`describe` and `it` are imported from the `node:test` module
+
+```mjs
+import { describe, it } from 'node:test';
+```
+
+```cjs
+const { describe, it } = require('node:test');
+```
+
 ### `only` tests
 
 If Node.js is started with the [`--test-only`][] command-line option, it is
@@ -303,7 +339,7 @@ added: v18.0.0
   * `todo` {boolean|string} If truthy, the test marked as `TODO`. If a string
     is provided, that string is displayed in the test results as the reason why
     the test is `TODO`. **Default:** `false`.
-* `fn` {Function|AsyncFunction} The function under test. This first argument
+* `fn` {Function|AsyncFunction} The function under test. The first argument
   to this function is a [`TestContext`][] object. If the test uses callbacks,
   the callback function is passed as the second argument. **Default:** A no-op
   function.
@@ -335,6 +371,59 @@ test('top level test', async (t) => {
 });
 ```
 
+## `describe([name][, options][, fn])`
+
+* `name` {string} The name of the suite, which is displayed when reporting test
+  results. **Default:** The `name` property of `fn`, or `'<anonymous>'` if `fn`
+  does not have a name.
+* `options` {Object} Configuration options for the suite.
+  supports the same options as `test([name][, options][, fn])`
+* `fn` {Function} The function under suite.
+  a synchronous function declaring all subtests and subsuites.
+  **Default:** A no-op function.
+* Returns: `undefined`.
+
+The `describe()` function imported from the `node:test` 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 `describe` functions,
+all top level tests and suites will execute
+
+## `describe.skip([name][, options][, fn])`
+
+Shorthand for skipping a suite, same as [`describe([name], { skip: true }[, fn])`][describe options].
+
+## `describe.todo([name][, options][, fn])`
+
+Shorthand for marking a suite as `TODO`, same as
+[`describe([name], { todo: true }[, fn])`][describe options].
+
+## `it([name][, options][, fn])`
+
+* `name` {string} The name of the test, which is displayed when reporting test
+  results. **Default:** The `name` property of `fn`, or `'<anonymous>'` if `fn`
+  does not have a name.
+* `options` {Object} Configuration options for the suite.
+  supports the same options as `test([name][, options][, fn])`.
+* `fn` {Function|AsyncFunction} The function under test.
+  If the test uses callbacks, the callback function is passed as an argument.
+  **Default:** A no-op function.
+* Returns: `undefined`.
+
+The `it()` function is the value imported from the `node:test` module.
+Each invocation of this function results in the creation of a test point in the
+TAP output.
+
+## `it.skip([name][, options][, fn])`
+
+Shorthand for skipping a test,
+same as [`it([name], { skip: true }[, fn])`][it options].
+
+## `it.todo([name][, options][, fn])`
+
+Shorthand for marking a test as `TODO`,
+same as [`it([name], { todo: true }[, fn])`][it options].
+
 ## Class: `TestContext`
 
 <!-- YAML
@@ -449,7 +538,7 @@ added: v18.0.0
   * `todo` {boolean|string} If truthy, the test marked as `TODO`. If a string
     is provided, that string is displayed in the test results as the reason why
     the test is `TODO`. **Default:** `false`.
-* `fn` {Function|AsyncFunction} The function under test. This first argument
+* `fn` {Function|AsyncFunction} The function under test. The first argument
   to this function is a [`TestContext`][] object. If the test uses callbacks,
   the callback function is passed as the second argument. **Default:** A no-op
   function.
@@ -475,4 +564,6 @@ test('top level test', async (t) => {
 [`--test`]: cli.md#--test
 [`TestContext`]: #class-testcontext
 [`test()`]: #testname-options-fn
+[describe options]: #describename-options-fn
+[it options]: #testname-options-fn
 [test runner execution model]: #test-runner-execution-model

lib/internal/main/test_runner.js

@@ -20,7 +20,7 @@ const {
     ERR_TEST_FAILURE,
   },
 } = require('internal/errors');
-const test = require('internal/test_runner/harness');
+const { test } = require('internal/test_runner/harness');
 const { kSubtestsFailed } = require('internal/test_runner/test');
 const {
   isSupportedFileType,

lib/internal/test_runner/harness.js

@@ -1,5 +1,9 @@
 'use strict';
-const { FunctionPrototypeBind, SafeMap } = primordials;
+const {
+  ArrayPrototypeForEach,
+  FunctionPrototypeBind,
+  SafeMap,
+} = primordials;
 const {
   createHook,
   executionAsyncId,
@@ -9,34 +13,43 @@ const {
     ERR_TEST_FAILURE,
   },
 } = require('internal/errors');
-const { Test } = require('internal/test_runner/test');
+const { Test, ItTest, Suite } = require('internal/test_runner/test');
+
+
+const testResources = new SafeMap();
+const root = new Test({ __proto__: null, name: '<root>' });
+let wasRootSetup = false;
 
-function createProcessEventHandler(eventName, rootTest, testResources) {
+function createProcessEventHandler(eventName, rootTest) {
   return (err) => {
     // Check if this error is coming from a test. If it is, fail the test.
     const test = testResources.get(executionAsyncId());
 
-    if (test !== undefined) {
-      if (test.finished) {
-        // If the test is already finished, report this as a top level
-        // diagnostic since this is a malformed test.
-        const msg = `Warning: Test "${test.name}" generated asynchronous ` +
-          'activity after the test ended. This activity created the error ' +
-          `"${err}" and would have caused the test to fail, but instead ` +
-          `triggered an ${eventName} event.`;
+    if (!test) {
+      throw err;
+    }
 
-        rootTest.diagnostic(msg);
-        return;
-      }
+    if (test.finished) {
+      // If the test is already finished, report this as a top level
+      // diagnostic since this is a malformed test.
+      const msg = `Warning: Test "${test.name}" generated asynchronous ` +
+        'activity after the test ended. This activity created the error ' +
+        `"${err}" and would have caused the test to fail, but instead ` +
+        `triggered an ${eventName} event.`;
 
-      test.fail(new ERR_TEST_FAILURE(err, eventName));
-      test.postRun();
+      rootTest.diagnostic(msg);
+      return;
     }
+
+    test.fail(new ERR_TEST_FAILURE(err, eventName));
+    test.postRun();
   };
 }
 
 function setup(root) {
-  const testResources = new SafeMap();
+  if (wasRootSetup) {
+    return root;
+  }
   const hook = createHook({
     init(asyncId, type, triggerAsyncId, resource) {
       if (resource instanceof Test) {
@@ -58,9 +71,9 @@ function setup(root) {
   hook.enable();
 
   const exceptionHandler =
-    createProcessEventHandler('uncaughtException', root, testResources);
+    createProcessEventHandler('uncaughtException', root);
   const rejectionHandler =
-    createProcessEventHandler('unhandledRejection', root, testResources);
+    createProcessEventHandler('unhandledRejection', root);
 
   process.on('uncaughtException', exceptionHandler);
   process.on('unhandledRejection', rejectionHandler);
@@ -113,19 +126,39 @@ function setup(root) {
 
   root.reporter.pipe(process.stdout);
   root.reporter.version();
+
+  wasRootSetup = true;
+  return root;
 }
 
 function test(name, options, fn) {
-  // If this is the first test encountered, bootstrap the test harness.
-  if (this.subtests.length === 0) {
-    setup(this);
+  const subtest = setup(root).createSubtest(Test, name, options, fn);
+  return subtest.start();
+}
+
+function runInParentContext(Factory) {
+  function run(name, options, fn, overrides) {
+    const parent = testResources.get(executionAsyncId()) || setup(root);
+    const subtest = parent.createSubtest(Factory, name, options, fn, overrides);
+    if (parent === root) {
+      subtest.start();
+    }
   }
 
-  const subtest = this.createSubtest(name, options, fn);
+  const cb = (name, options, fn) => {
+    run(name, options, fn);
+  };
 
-  return subtest.start();
+  ArrayPrototypeForEach(['skip', 'todo'], (keyword) => {
+    cb[keyword] = (name, options, fn) => {
+      run(name, options, fn, { [keyword]: true });
+    };
+  });
+  return cb;
 }
 
-const root = new Test({ name: '<root>' });
-
-module.exports = FunctionPrototypeBind(test, root);
+module.exports = {
+  test: FunctionPrototypeBind(test, root),
+  describe: runInParentContext(Suite),
+  it: runInParentContext(ItTest),
+};