test_runner: add testId to test events

doc/api/test.md

@@ -3431,6 +3431,9 @@ Emitted when code coverage is enabled and all tests have completed.
     `undefined` if the test was run through the REPL.
   * `name` {string} The test name.
   * `nesting` {number} The nesting level of the test.
+  * `testId` {number} A numeric identifier for this test instance, unique
+    within the test file's process. Consistent across all events for the same
+    test instance, enabling reliable correlation in custom reporters.
   * `testNumber` {number} The ordinal number of the test.
   * `todo` {string|boolean|undefined} Present if [`context.todo`][] is called
   * `skip` {string|boolean|undefined} Present if [`context.skip`][] is called
@@ -3451,6 +3454,9 @@ The corresponding declaration ordered events are `'test:pass'` and `'test:fail'`
     `undefined` if the test was run through the REPL.
   * `name` {string} The test name.
   * `nesting` {number} The nesting level of the test.
+  * `testId` {number} A numeric identifier for this test instance, unique
+    within the test file's process. Consistent across all events for the same
+    test instance, enabling reliable correlation in custom reporters.
   * `type` {string} The test type. Either `'suite'` or `'test'`.
 
 Emitted when a test is dequeued, right before it is executed.
@@ -3489,6 +3495,9 @@ defined.
     `undefined` if the test was run through the REPL.
   * `name` {string} The test name.
   * `nesting` {number} The nesting level of the test.
+  * `testId` {number} A numeric identifier for this test instance, unique
+    within the test file's process. Consistent across all events for the same
+    test instance, enabling reliable correlation in custom reporters.
   * `type` {string} The test type. Either `'suite'` or `'test'`.
 
 Emitted when a test is enqueued for execution.
@@ -3512,6 +3521,9 @@ Emitted when a test is enqueued for execution.
     `undefined` if the test was run through the REPL.
   * `name` {string} The test name.
   * `nesting` {number} The nesting level of the test.
+  * `testId` {number} A numeric identifier for this test instance, unique
+    within the test file's process. Consistent across all events for the same
+    test instance, enabling reliable correlation in custom reporters.
   * `testNumber` {number} The ordinal number of the test.
   * `todo` {string|boolean|undefined} Present if [`context.todo`][] is called
   * `skip` {string|boolean|undefined} Present if [`context.skip`][] is called
@@ -3568,6 +3580,9 @@ since the parent runner only knows about file-level tests. When using
     `undefined` if the test was run through the REPL.
   * `name` {string} The test name.
   * `nesting` {number} The nesting level of the test.
+  * `testId` {number} A numeric identifier for this test instance, unique
+    within the test file's process. Consistent across all events for the same
+    test instance, enabling reliable correlation in custom reporters.
   * `testNumber` {number} The ordinal number of the test.
   * `todo` {string|boolean|undefined} Present if [`context.todo`][] is called
   * `skip` {string|boolean|undefined} Present if [`context.skip`][] is called
@@ -3604,6 +3619,9 @@ defined.
     `undefined` if the test was run through the REPL.
   * `name` {string} The test name.
   * `nesting` {number} The nesting level of the test.
+  * `testId` {number} A numeric identifier for this test instance, unique
+    within the test file's process. Consistent across all events for the same
+    test instance, enabling reliable correlation in custom reporters.
 
 Emitted when a test starts reporting its own and its subtests status.
 This event is guaranteed to be emitted in the same order as the tests are

lib/internal/test_runner/test.js

@@ -590,6 +590,8 @@ class Test extends AsyncResource {
       this.timeout = kDefaultTimeout;
       this.entryFile = entryFile;
       this.testDisambiguator = new SafeMap();
+      this.nextTestId = 1;
+      this.testId = 0;
     } else {
       const nesting = parent.parent === null ? parent.nesting :
         parent.nesting + 1;
@@ -606,6 +608,7 @@ class Test extends AsyncResource {
       this.childNumber = parent.subtests.length + 1;
       this.timeout = parent.timeout;
       this.entryFile = parent.entryFile;
+      this.testId = this.root.nextTestId++;
 
       if (isFilteringByName) {
         this.filteredByName = this.willBeFilteredByName();
@@ -884,7 +887,7 @@ class Test extends AsyncResource {
       const deferred = this.dequeuePendingSubtest();
       const test = deferred.test;
       this.assignReportOrder(test);
-      test.reporter.dequeue(test.nesting, test.loc, test.name, this.reportedType);
+      test.reporter.dequeue(test.nesting, test.loc, test.name, this.reportedType, test.testId);
       await test.run();
       deferred.resolve();
     }
@@ -1141,7 +1144,7 @@ class Test extends AsyncResource {
     // it. Otherwise, return a Promise to the caller and mark the test as
     // pending for later execution.
     this.parent.unfinishedSubtests.add(this);
-    this.reporter.enqueue(this.nesting, this.loc, this.name, this.reportedType);
+    this.reporter.enqueue(this.nesting, this.loc, this.name, this.reportedType, this.testId);
     if (this.root.harness.buildPromise || !this.parent.hasConcurrency()) {
       const deferred = PromiseWithResolvers();
 
@@ -1164,7 +1167,7 @@ class Test extends AsyncResource {
     }
 
     this.parent.assignReportOrder(this);
-    this.reporter.dequeue(this.nesting, this.loc, this.name, this.reportedType);
+    this.reporter.dequeue(this.nesting, this.loc, this.name, this.reportedType, this.testId);
     return this.run();
   }
 
@@ -1426,7 +1429,10 @@ class Test extends AsyncResource {
         const report = this.getReportDetails();
         report.details.passed = this.passed;
         this.testNumber ||= ++this.parent.outputSubtestCount;
-        this.reporter.complete(this.nesting, this.loc, this.testNumber, this.name, report.details, report.directive);
+        this.reporter.complete(
+          this.nesting, this.loc, this.testNumber, this.name,
+          report.details, report.directive, this.testId,
+        );
         this.parent.activeSubtests--;
       }
 
@@ -1579,9 +1585,15 @@ class Test extends AsyncResource {
     const report = this.getReportDetails();
 
     if (this.passed) {
-      this.reporter.ok(this.nesting, this.loc, this.testNumber, this.name, report.details, report.directive);
+      this.reporter.ok(
+        this.nesting, this.loc, this.testNumber, this.name,
+        report.details, report.directive, this.testId,
+      );
     } else {
-      this.reporter.fail(this.nesting, this.loc, this.testNumber, this.name, report.details, report.directive);
+      this.reporter.fail(
+        this.nesting, this.loc, this.testNumber, this.name,
+        report.details, report.directive, this.testId,
+      );
     }
 
     for (let i = 0; i < this.diagnostics.length; i++) {
@@ -1595,7 +1607,7 @@ class Test extends AsyncResource {
     }
     this.#reportedSubtest = true;
     this.parent.reportStarted();
-    this.reporter.start(this.nesting, this.loc, this.name);
+    this.reporter.start(this.nesting, this.loc, this.name, this.testId);
   }
 
   clearExecutionTime() {

lib/internal/test_runner/tests_stream.js

@@ -34,36 +34,39 @@ class TestsStream extends Readable {
     }
   }
 
-  fail(nesting, loc, testNumber, name, details, directive) {
+  fail(nesting, loc, testNumber, name, details, directive, testId) {
     this[kEmitMessage]('test:fail', {
       __proto__: null,
       name,
       nesting,
       testNumber,
+      testId,
       details,
       ...loc,
       ...directive,
     });
   }
 
-  ok(nesting, loc, testNumber, name, details, directive) {
+  ok(nesting, loc, testNumber, name, details, directive, testId) {
     this[kEmitMessage]('test:pass', {
       __proto__: null,
       name,
       nesting,
       testNumber,
+      testId,
       details,
       ...loc,
       ...directive,
     });
   }
 
-  complete(nesting, loc, testNumber, name, details, directive) {
+  complete(nesting, loc, testNumber, name, details, directive, testId) {
     this[kEmitMessage]('test:complete', {
       __proto__: null,
       name,
       nesting,
       testNumber,
+      testId,
       details,
       ...loc,
       ...directive,
@@ -91,31 +94,34 @@ class TestsStream extends Readable {
     return { __proto__: null, expectFailure: expectation ?? true };
   }
 
-  enqueue(nesting, loc, name, type) {
+  enqueue(nesting, loc, name, type, testId) {
     this[kEmitMessage]('test:enqueue', {
       __proto__: null,
       nesting,
       name,
       type,
+      testId,
       ...loc,
     });
   }
 
-  dequeue(nesting, loc, name, type) {
+  dequeue(nesting, loc, name, type, testId) {
     this[kEmitMessage]('test:dequeue', {
       __proto__: null,
       nesting,
       name,
       type,
+      testId,
       ...loc,
     });
   }
 
-  start(nesting, loc, name) {
+  start(nesting, loc, name, testId) {
     this[kEmitMessage]('test:start', {
       __proto__: null,
       nesting,
       name,
+      testId,
       ...loc,
     });
   }

test/fixtures/test-runner/test-id-fixture.js

@@ -0,0 +1,21 @@
+'use strict';
+const { describe, it } = require('node:test');
+const assert = require('node:assert');
+
+// Factory that creates subtests at the SAME source location.
+// Multiple concurrent `it` blocks calling this will have subtests
+// sharing file:line:column — but each should get a distinct testId.
+function makeSubtest(shouldFail) {
+  return async function(t) {
+    await t.test('e2e', async () => {
+      if (shouldFail) assert.fail('intentional');
+    });
+  };
+}
+
+describe('suite', { concurrency: 10_000 }, () => {
+  it('test-A (passes)', makeSubtest(false));
+  it('test-B (passes)', makeSubtest(false));
+  it('test-C (fails)', makeSubtest(true));
+  it('test-D (passes)', makeSubtest(false));
+});

test/parallel/test-runner-test-id.js

@@ -0,0 +1,76 @@
+'use strict';
+require('../common');
+const assert = require('node:assert');
+const { run } = require('node:test');
+const fixtures = require('../common/fixtures');
+
+async function collectEvents() {
+  const events = [];
+  const stream = run({
+    files: [fixtures.path('test-runner/test-id-fixture.js')],
+    isolation: 'none',
+  });
+  for await (const event of stream) {
+    events.push(event);
+  }
+  return events;
+}
+
+async function main() {
+  const events = await collectEvents();
+
+  // 1. Every per-test event should have a numeric testId.
+  const perTestTypes = new Set([
+    'test:start', 'test:complete', 'test:fail',
+    'test:pass', 'test:enqueue', 'test:dequeue',
+  ]);
+  for (const event of events) {
+    if (perTestTypes.has(event.type)) {
+      assert.strictEqual(typeof event.data.testId, 'number',
+                         `${event.type} for "${event.data.name}" should have numeric testId`);
+    }
+  }
+
+  // 2. test:start and test:fail for the same instance should share testId.
+  const failEvent = events.find(
+    (e) => e.type === 'test:fail' && e.data.name === 'e2e',
+  );
+  assert.ok(failEvent, 'should have a test:fail for "e2e"');
+
+  const startEvent = events.find(
+    (e) => e.type === 'test:start' &&
+           e.data.testId === failEvent.data.testId,
+  );
+  assert.ok(startEvent, 'should have a test:start with matching testId');
+  assert.strictEqual(startEvent.data.name, 'e2e');
+
+  // 3. Concurrent instances at the same source location get distinct testIds.
+  const e2eStarts = events.filter(
+    (e) => e.type === 'test:start' && e.data.name === 'e2e',
+  );
+  assert.strictEqual(e2eStarts.length, 4);
+
+  const testIds = e2eStarts.map((e) => e.data.testId);
+  const uniqueIds = new Set(testIds);
+  assert.strictEqual(uniqueIds.size, 4,
+                     `all 4 "e2e" instances should have distinct testIds, got: ${testIds}`);
+
+  // 4. test:complete for the same instance shares testId with test:start.
+  const completeEvents = events.filter(
+    (e) => e.type === 'test:complete' && e.data.name === 'e2e',
+  );
+  for (const complete of completeEvents) {
+    const matchingStart = e2eStarts.find(
+      (s) => s.data.testId === complete.data.testId,
+    );
+    assert.ok(matchingStart,
+              `test:complete (testId=${complete.data.testId}) should match a test:start`);
+  }
+
+  console.log('All testId assertions passed');
+}
+
+main().catch((err) => {
+  console.error(err);
+  process.exit(1);
+});