test_runner: fix Date serialization in TAP reporter YAML output

lib/internal/test_runner/reporter/tap.js

@@ -167,6 +167,8 @@ function jsToYaml(indent, name, value, seen) {
     if (internalBinding('types').isDate(value)) {
       // YAML uses the ISO-8601 standard to express dates.
       result += ' ' + DatePrototypeToISOString(value);
+      result += '\n';
+      return result; // Early return to prevent processing Date as object
     }
     result += '\n';
     propsIndent += '  ';

test/fixtures/test-runner/output/tap_date_serialization.js

@@ -0,0 +1,31 @@
+// Flags: --test-reporter=tap
+'use strict';
+const { test } = require('node:test');
+const assert = require('node:assert');
+
+// Test Date vs Date comparison
+test('date vs date comparison', () => {
+  const expected = new Date('2023-01-01T12:00:00.000Z');
+  const actual = new Date('2023-01-01T13:00:00.000Z');
+  assert.deepStrictEqual(actual, expected);
+});
+
+// Test Date vs String comparison
+test('date vs string comparison', () => {
+  const expected = '2023-01-01T12:00:00.000Z';
+  const actual = new Date('2023-01-01T13:00:00.000Z');
+  assert.deepStrictEqual(actual, expected);
+});
+
+// Test nested Date objects
+test('nested date objects', () => {
+  const expected = {
+    timestamp: new Date('2023-01-01T12:00:00.000Z'),
+    message: 'test'
+  };
+  const actual = {
+    timestamp: new Date('2023-01-01T13:00:00.000Z'),
+    message: 'test'
+  };
+  assert.deepStrictEqual(actual, expected);
+}); 

test/fixtures/test-runner/output/tap_date_serialization.snapshot

@@ -0,0 +1,99 @@
+TAP version 13
+# Subtest: date vs date comparison
+not ok 1 - date vs date comparison
+  ---
+  duration_ms: *
+  type: 'test'
+  location: '*test-runner*tap_date_serialization.js:7:1'
+  failureType: 'testCodeFailure'
+  error: |-
+    Expected values to be strictly deep-equal:
+    + actual - expected
+
+    + 2023-01-01T13:00:00.000Z
+    - 2023-01-01T12:00:00.000Z
+
+  code: 'ERR_ASSERTION'
+  name: 'AssertionError'
+  expected: 2023-01-01T12:00:00.000Z
+  actual: 2023-01-01T13:00:00.000Z
+  operator: 'deepStrictEqual'
+  stack: |-
+    TestContext.<anonymous> (*test-runner*tap_date_serialization.js:10:10)
+    Test.runInAsyncScope (node:async_hooks:214:14)
+    Test.run (node:internal/test_runner/test:1047:25)
+    Test.start (node:internal/test_runner/test:944:17)
+    startSubtestAfterBootstrap (node:internal/test_runner/harness:297:17)
+  ...
+# Subtest: date vs string comparison
+not ok 2 - date vs string comparison
+  ---
+  duration_ms: *
+  type: 'test'
+  location: '*test-runner*tap_date_serialization.js:14:1'
+  failureType: 'testCodeFailure'
+  error: |-
+    Expected values to be strictly deep-equal:
+    + actual - expected
+
+    + 2023-01-01T13:00:00.000Z
+    - '2023-01-01T12:00:00.000Z'
+
+  code: 'ERR_ASSERTION'
+  name: 'AssertionError'
+  expected: '2023-01-01T12:00:00.000Z'
+  actual: 2023-01-01T13:00:00.000Z
+  operator: 'deepStrictEqual'
+  stack: |-
+    TestContext.<anonymous> (*test-runner*tap_date_serialization.js:17:10)
+    Test.runInAsyncScope (node:async_hooks:214:14)
+    Test.run (node:internal/test_runner/test:1047:25)
+    Test.processPendingSubtests (node:internal/test_runner/test:744:18)
+    Test.postRun (node:internal/test_runner/test:1173:19)
+    Test.run (node:internal/test_runner/test:1101:12)
+    async startSubtestAfterBootstrap (node:internal/test_runner/harness:297:3)
+  ...
+# Subtest: nested date objects
+not ok 3 - nested date objects
+  ---
+  duration_ms: *
+  type: 'test'
+  location: '*test-runner*tap_date_serialization.js:21:1'
+  failureType: 'testCodeFailure'
+  error: |-
+    Expected values to be strictly deep-equal:
+    + actual - expected
+
+      {
+        message: 'test',
+    +   timestamp: 2023-01-01T13:00:00.000Z
+    -   timestamp: 2023-01-01T12:00:00.000Z
+      }
+
+  code: 'ERR_ASSERTION'
+  name: 'AssertionError'
+  expected:
+    timestamp: 2023-01-01T12:00:00.000Z
+    message: 'test'
+  actual:
+    timestamp: 2023-01-01T13:00:00.000Z
+    message: 'test'
+  operator: 'deepStrictEqual'
+  stack: |-
+    TestContext.<anonymous> (*test-runner*tap_date_serialization.js:30:10)
+    Test.runInAsyncScope (node:async_hooks:214:14)
+    Test.run (node:internal/test_runner/test:1047:25)
+    Test.processPendingSubtests (node:internal/test_runner/test:744:18)
+    Test.postRun (node:internal/test_runner/test:1173:19)
+    Test.run (node:internal/test_runner/test:1101:12)
+    async Test.processPendingSubtests (node:internal/test_runner/test:744:7)
+  ...
+1..3
+# tests 3
+# suites 0
+# pass 0
+# fail 3
+# cancelled 0
+# skipped 0
+# todo 0
+# duration_ms * 

test/parallel/test-runner-output.mjs

@@ -240,6 +240,14 @@ const tests = [
     ),
     flags: ['--test-reporter=tap'],
   },
+  {
+    name: 'test-runner/output/tap_date_serialization.js',
+    transform: snapshot.transform(
+      snapshot.replaceWindowsLineEndings,
+      replaceTestDuration,
+    ),
+    flags: ['--test-reporter=tap'],
+  },
   {
     name: 'test-runner/output/test-runner-plan.js',
     flags: ['--test-reporter=tap'],

test/parallel/test-tap-yaml-date-serialization.js

@@ -0,0 +1,21 @@
+'use strict';
+
+// This file documents that Date serialization in TAP reporter YAML output
+// is tested via the fixture test: test/fixtures/test-runner/output/tap_date_serialization.js
+// 
+// The fixture test verifies that:
+// 1. Date objects are serialized as clean ISO strings (e.g., "2023-01-01T12:00:00.000Z")
+// 2. Date vs String comparisons show clear distinction (Date vs '2023-01-01T12:00:00.000Z')  
+// 3. Nested Date objects in error details are properly serialized
+// 4. Date objects do NOT include their methods/properties (getTime, valueOf, etc.)
+//
+// This behavioral testing approach is more robust than testing implementation details
+// and is resistant to code refactoring.
+
+const { test } = require('node:test');
+
+// Simple placeholder test to ensure this file is valid
+test('Date serialization is tested via fixture', () => {
+  // The actual testing is done via test/fixtures/test-runner/output/tap_date_serialization.js
+  // and verified against test/fixtures/test-runner/output/tap_date_serialization.snapshot
+});