test_runner: update test + update docs

doc/api/test.md

@@ -333,10 +333,11 @@ changes:
   properties are supported:
   * `concurrency` {number|boolean} If a number is provided,
     then that many tests would run in parallel.
-    If truthy, on top level, it would run (number of cpu cores - 1)
-    tests in parallel.
+    If truthy, when running in `--test` mode, it would run
+    (number of cpu cores - 1) tests in parallel.
     For subtests, it will be infinity tests in parallel.
-    If falsy, on top level & subtest level it would only run one test at a time.
+    If falsy, when running in `--test` mode & subtest level
+    it would only run one test at a time.
     If unspecified, subtests inherit this value from their parent.
     **Default:** `1`.
   * `only` {boolean} If truthy, and the test context is configured to run

test/message/test_runner_describe_it.js

@@ -339,47 +339,3 @@ describe('timeouts', () => {
     setTimeout(done, 10);
   });
 });
-
-describe('Concurrency option (boolean) = true ', { concurrency: true }, () => {
-  const suiteStartDateTime = new Date().getTime();
-  const extraBufferTime = 10;
-  it('should be over by 3 seconds from suite start', async () => {
-    const duration = 3000;
-    const expectedEndDateTime = suiteStartDateTime + duration + extraBufferTime;
-    await new Promise((resolve, reject) => {
-      setTimeout(resolve, duration);
-    });
-    assert.strictEqual(expectedEndDateTime > new Date().getTime(), true);
-  });
-  it('should be over by 1 second from suite start', async () => {
-    const duration = 1000;
-    const expectedEndDateTime = suiteStartDateTime + duration + extraBufferTime;
-    await new Promise((resolve, reject) => {
-      setTimeout(resolve, duration);
-    });
-    assert.strictEqual(expectedEndDateTime > new Date().getTime(), true);
-  });
-});
-
-describe('Concurrency option (boolean) = false ', { concurrency: false }, () => {
-  const suiteStartDateTime = new Date().getTime();
-  const extraBufferTime = 10;
-  it('should be over by 3 seconds from suite start', async () => {
-    const duration = 3000;
-    const expectedEndDateTime = suiteStartDateTime + duration + extraBufferTime;
-    await new Promise((resolve, reject) => {
-      setTimeout(resolve, duration);
-    });
-    assert.strictEqual(expectedEndDateTime > new Date().getTime(), true);
-  });
-  it('should be over by 4 seconds from suite start', async () => {
-    const duration = 1000;
-    const prevTestDuration = 3000;
-    const expectedEndDateTime =
-      suiteStartDateTime + duration + extraBufferTime + prevTestDuration;
-    await new Promise((resolve, reject) => {
-      setTimeout(resolve, duration);
-    });
-    assert.strictEqual(expectedEndDateTime > new Date().getTime(), true);
-  });
-});

test/parallel/test-runner-concurrency.js

@@ -0,0 +1,28 @@
+'use strict';
+require('../common');
+const { describe, it } = require('node:test');
+const assert = require('assert');
+
+describe('Concurrency option (boolean) = true ', { concurrency: true }, () => {
+  let isFirstTestOver = false;
+  it('should end after 1000ms', () => new Promise((resolve) => {
+    setTimeout(() => { resolve(); isFirstTestOver = true; }, 1000);
+  }));
+  it('should start before the previous test ends', () => {
+    assert.strictEqual(isFirstTestOver, false);
+  });
+});
+
+describe(
+  'Concurrency option (boolean) = false ',
+  { concurrency: false },
+  () => {
+    let isFirstTestOver = false;
+    it('should end after 1000ms', () => new Promise((resolve) => {
+      setTimeout(() => { resolve(); isFirstTestOver = true; }, 1000);
+    }));
+    it('should start after the previous test ends', () => {
+      assert.strictEqual(isFirstTestOver, true);
+    });
+  }
+);