test_runner: publish to TracingChannel for OTel instrumentation

Signed-off-by: Moshe Atlow <moshe@atlow.co.il>
PR-URL: #62502
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>
Reviewed-By: Chemi Atlow <chemi@atlow.co.il>

Author: MoLow

doc/api/test.md

@@ -3701,6 +3701,91 @@ When called from within a hook (before, beforeEach, after, afterEach), this
 function returns the context of the test or suite that the hook is associated
 with.
 
+## Test instrumentation and OpenTelemetry
+
+<!-- YAML
+added: REPLACEME
+-->
+
+The test runner publishes test execution events through the Node.js
+[`diagnostics_channel`][] module, enabling integration with observability tools
+like OpenTelemetry without requiring changes to the test runner itself.
+
+### Tracing events
+
+The test runner publishes events to the `'node.test'` tracing channel. Subscribers
+can use the [`TracingChannel`][] API to bind context or perform custom
+instrumentation.
+
+#### Channel: `'tracing:node.test:start'`
+
+* `data` {Object}
+  * `name` {string} The name of the test.
+  * `nesting` {number} The nesting level of the test.
+  * `file` {string|undefined} The path to the test file, or `undefined` when
+    running in the REPL.
+  * `type` {string} The type of test. Either `'test'` or `'suite'`.
+
+Emitted when a test or suite starts execution. The test's span encompasses all
+of its before, beforeEach, and afterEach hooks, as well as the test body.
+
+#### Channel: `'tracing:node.test:end'`
+
+* `data` {Object}
+  * `name` {string} The name of the test.
+  * `nesting` {number} The nesting level of the test.
+  * `file` {string|undefined} The path to the test file, or `undefined` when
+    running in the REPL.
+  * `type` {string} The type of test. Either `'test'` or `'suite'`.
+
+Emitted when a test or suite finishes execution.
+
+#### Channel: `'tracing:node.test:error'`
+
+* `data` {Object}
+  * `name` {string} The name of the test.
+  * `nesting` {number} The nesting level of the test.
+  * `file` {string|undefined} The path to the test file, or `undefined` when
+    running in the REPL.
+  * `type` {string} The type of test. Either `'test'` or `'suite'`.
+  * `error` {Error} The error that was thrown.
+
+Emitted when a test or suite throws an error.
+
+### Context propagation with `bindStore()`
+
+The tracing channel can be used to propagate context through test execution by
+binding an `AsyncLocalStorage` instance. This allows context to be automatically
+available in the test function and all async operations within the test.
+
+```mjs
+import dc from 'node:diagnostics_channel';
+import { AsyncLocalStorage } from 'node:async_hooks';
+
+const testStorage = new AsyncLocalStorage();
+const testChannel = dc.tracingChannel('node.test');
+
+// Bind context to test execution — the returned value becomes the store
+testChannel.start.bindStore(testStorage, (data) => {
+  return { testName: data.name, startTime: Date.now() };
+});
+
+// Optionally handle errors and cleanup
+testChannel.error.subscribe((data) => {
+  const store = testStorage.getStore();
+  console.log(`Test "${data.name}" failed after ${Date.now() - store.startTime}ms`);
+});
+
+testChannel.end.subscribe((data) => {
+  const store = testStorage.getStore();
+  console.log(`Test "${data.name}" completed in ${Date.now() - store.startTime}ms`);
+});
+```
+
+When using `bindStore()`, the context provided will be automatically propagated
+to the test function and all async operations within the test, without requiring
+any additional instrumentation in the test code.
+
 ## Class: `TestContext`
 
 <!-- YAML
@@ -4433,11 +4518,13 @@ test.describe('my suite', (suite) => {
 [`NODE_V8_COVERAGE`]: cli.md#node_v8_coveragedir
 [`SuiteContext`]: #class-suitecontext
 [`TestContext`]: #class-testcontext
+[`TracingChannel`]: diagnostics_channel.md#class-tracingchannel
 [`assert.throws`]: assert.md#assertthrowsfn-error-message
 [`context.diagnostic`]: #contextdiagnosticmessage
 [`context.skip`]: #contextskipmessage
 [`context.todo`]: #contexttodomessage
 [`describe()`]: #describename-options-fn
+[`diagnostics_channel`]: diagnostics_channel.md
 [`glob(7)`]: https://man7.org/linux/man-pages/man7/glob.7.html
 [`it()`]: #itname-options-fn
 [`run()`]: #runoptions

lib/internal/test_runner/test.js

@@ -55,6 +55,7 @@ const {
   countCompletedTest,
   isTestFailureError,
   reporterScope,
+  testChannel,
 } = require('internal/test_runner/utils');
 const {
   kEmptyObject,
@@ -1211,6 +1212,17 @@ class Test extends AsyncResource {
     }
     this.startTime ??= hrtime();
 
+    // Channel context object shared across all lifecycle events for this test run.
+    // Only tests emit events; hooks do not. This way, the test's span encompasses
+    // its before/beforeEach hooks, the test body, and its afterEach/after hooks.
+    const channelContext = this.hookType === undefined ? {
+      __proto__: null,
+      name: this.name,
+      nesting: this.nesting,
+      file: this.entryFile,
+      type: this.reportedType,
+    } : null;
+
     if (this[kShouldAbort]()) {
       this.postRun();
       return;
@@ -1248,7 +1260,20 @@ class Test extends AsyncResource {
       }
       stopPromise = stopTest(this.timeout, this.signal);
       const runArgs = ArrayPrototypeSlice(args);
-      ArrayPrototypeUnshift(runArgs, this.fn, ctx);
+
+      // Wrap the test function with runStores if the channel has subscribers.
+      // The wrapped function is what gets passed to runInAsyncScope, ensuring that
+      // the test runs within both the runStores context (for AsyncLocalStorage/bindStore)
+      // AND the AsyncResource scope. It's critical that runStores wraps the function,
+      // not the runInAsyncScope call itself, to maintain AsyncLocalStorage bindings.
+      let testFn = this.fn;
+      if (channelContext !== null && testChannel.start.hasSubscribers) {
+        testFn = (...fnArgs) => testChannel.start.runStores(channelContext,
+                                                            () => ReflectApply(this.fn, this, fnArgs),
+        );
+      }
+
+      ArrayPrototypeUnshift(runArgs, testFn, ctx);
 
       const promises = [];
       if (this.fn.length === runArgs.length - 1) {
@@ -1297,6 +1322,10 @@ class Test extends AsyncResource {
       await afterEach();
       await after();
     } catch (err) {
+      // Publish diagnostics_channel error event if the channel has subscribers
+      if (channelContext !== null && testChannel.error.hasSubscribers) {
+        testChannel.error.publish({ __proto__: null, ...channelContext, error: err });
+      }
       if (isTestFailureError(err)) {
         if (err.failureType === kTestTimeoutFailure) {
           this.#cancel(err);
@@ -1316,6 +1345,11 @@ class Test extends AsyncResource {
       if (this.parent !== null) {
         this.abortController.abort();
       }
+
+      // Publish diagnostics_channel end event if the channel has subscribers (in both success and error cases)
+      if (channelContext !== null && testChannel.end.hasSubscribers) {
+        testChannel.end.publish(channelContext);
+      }
     }
 
     if (this.parent !== null || typeof this.hookType === 'string') {
@@ -1643,13 +1677,42 @@ class Suite extends Test {
   }
 
   async createBuild() {
+    const channelContext = {
+      __proto__: null,
+      name: this.name,
+      nesting: this.nesting,
+      file: this.entryFile,
+      type: this.reportedType,
+    };
     try {
       const { ctx, args } = this.getRunArgs();
-      const runArgs = [this.fn, ctx];
+
+      // Wrap the suite function with runStores if the channel has subscribers.
+      // The wrapped function is what gets passed to runInAsyncScope, ensuring that
+      // the suite runs within both the runStores context (for AsyncLocalStorage/bindStore)
+      // AND the AsyncResource scope. It's critical that runStores wraps the function,
+      // not the runInAsyncScope call itself, to maintain AsyncLocalStorage bindings.
+      let suiteFn = this.fn;
+      if (testChannel.start.hasSubscribers) {
+        const baseFn = this.fn;
+        suiteFn = (...fnArgs) => testChannel.start.runStores(channelContext,
+                                                             () => ReflectApply(baseFn, this, fnArgs),
+        );
+      }
+
+      const runArgs = [suiteFn, ctx];
       ArrayPrototypePushApply(runArgs, args);
+
       await ReflectApply(this.runInAsyncScope, this, runArgs);
     } catch (err) {
+      if (testChannel.error.hasSubscribers) {
+        testChannel.error.publish({ __proto__: null, ...channelContext, error: err });
+      }
       this.fail(new ERR_TEST_FAILURE(err, kTestCodeFailure));
+    } finally {
+      if (testChannel.end.hasSubscribers) {
+        testChannel.end.publish(channelContext);
+      }
     }
 
     this.buildPhaseFinished = true;

lib/internal/test_runner/utils.js

@@ -31,6 +31,7 @@ const {
 } = primordials;
 
 const { AsyncResource } = require('async_hooks');
+const { tracingChannel } = require('diagnostics_channel');
 const { relative, sep, resolve } = require('path');
 const { createWriteStream, readFileSync } = require('fs');
 const { pathToFileURL } = require('internal/url');
@@ -256,6 +257,7 @@ async function getReportersMap(reporters, destinations) {
 }
 
 const reporterScope = new AsyncResource('TestReporterScope');
+const testChannel = tracingChannel('node.test');
 let globalTestOptions;
 
 function parseCommandLine() {
@@ -730,4 +732,5 @@ module.exports = {
   getCoverageReport,
   setupGlobalSetupTeardownFunctions,
   parsePreviousRuns,
+  testChannel,
 };

test/fixtures/test-runner/diagnostics-channel-error-test.js

@@ -0,0 +1,17 @@
+'use strict';
+const dc = require('node:diagnostics_channel');
+const { test } = require('node:test');
+
+const events = [];
+dc.subscribe('tracing:node.test:error', (data) => {
+  events.push(data.name);
+});
+
+test('test that intentionally fails', async () => {
+  throw new Error('expected failure for error event testing');
+});
+
+// Report events on exit
+process.on('exit', () => {
+  console.log(JSON.stringify({ errorEvents: events }));
+});

test/parallel/test-runner-diagnostics-channel.js

@@ -0,0 +1,137 @@
+'use strict';
+require('../common');
+const assert = require('node:assert');
+const { AsyncLocalStorage } = require('node:async_hooks');
+const dc = require('node:diagnostics_channel');
+const { describe, it, test } = require('node:test');
+const { spawnSync } = require('child_process');
+const { join } = require('path');
+
+const events = [];
+
+dc.subscribe('tracing:node.test:start', (data) => events.push({ event: 'start', name: data.name }));
+dc.subscribe('tracing:node.test:end', (data) => events.push({ event: 'end', name: data.name }));
+dc.subscribe('tracing:node.test:error', (data) => events.push({ event: 'error', name: data.name }));
+
+test('passing test fires start and end', async () => {});
+
+// Validate events were emitted (check after all tests via process.on('exit'))
+process.on('exit', () => {
+  // Check passing test
+  const testName1 = 'passing test fires start and end';
+  const startEvents = events.filter((e) => e.event === 'start' && e.name === testName1);
+  const endEvents = events.filter((e) => e.event === 'end' && e.name === testName1);
+  assert.strictEqual(startEvents.length, 1);
+  assert.strictEqual(endEvents.length, 1);
+
+  // Check nested tests fire events
+  const nested1Start = events.filter((e) => e.event === 'start' && e.name === 'nested test 1');
+  const nested1End = events.filter((e) => e.event === 'end' && e.name === 'nested test 1');
+  const nested2Start = events.filter((e) => e.event === 'start' && e.name === 'nested test 2');
+  const nested2End = events.filter((e) => e.event === 'end' && e.name === 'nested test 2');
+  assert.strictEqual(nested1Start.length, 1);
+  assert.strictEqual(nested1End.length, 1);
+  assert.strictEqual(nested2Start.length, 1);
+  assert.strictEqual(nested2End.length, 1);
+
+  // Check describe block tests fire events
+  const describeStart = events.filter((e) => e.event === 'start' && e.name === 'test inside describe');
+  const describeEnd = events.filter((e) => e.event === 'end' && e.name === 'test inside describe');
+  const describeStart2 = events.filter(
+    (e) => e.event === 'start' && e.name === 'another test inside describe',
+  );
+  const describeEnd2 = events.filter(
+    (e) => e.event === 'end' && e.name === 'another test inside describe',
+  );
+  assert.strictEqual(describeStart.length, 1);
+  assert.strictEqual(describeEnd.length, 1);
+  assert.strictEqual(describeStart2.length, 1);
+  assert.strictEqual(describeEnd2.length, 1);
+
+  // Check async operations test fires events
+  const asyncTestName = 'context is available in async operations within test';
+  const asyncStart = events.filter((e) => e.event === 'start' && e.name === asyncTestName);
+  const asyncEnd = events.filter((e) => e.event === 'end' && e.name === asyncTestName);
+  assert.strictEqual(asyncStart.length, 1);
+  assert.strictEqual(asyncEnd.length, 1);
+});
+
+// Test bindStore context propagation
+const testStorage = new AsyncLocalStorage();
+
+// bindStore on the start channel: whenever a test fn runs, set testStorage to the test name
+dc.channel('tracing:node.test:start').bindStore(testStorage, (data) => data.name);
+
+const expectedName = 'bindStore propagates into test body via start channel';
+test(expectedName, async () => {
+  const storedValueDuringTest = testStorage.getStore();
+  assert.strictEqual(storedValueDuringTest, expectedName);
+
+  // Propagates into async operations inside the test
+  const valueInSetImmediate = await new Promise((resolve) => {
+    setImmediate(() => resolve(testStorage.getStore()));
+  });
+  assert.strictEqual(valueInSetImmediate, expectedName);
+});
+
+test('bindStore value is isolated between tests', async () => {
+  assert.strictEqual(testStorage.getStore(), 'bindStore value is isolated between tests');
+});
+
+test('nested tests fire events with correct names', async (t) => {
+  await t.test('nested test 1', async () => {
+    const stored = testStorage.getStore();
+    assert.strictEqual(stored, 'nested test 1');
+  });
+
+  await t.test('nested test 2', async () => {
+    const stored = testStorage.getStore();
+    assert.strictEqual(stored, 'nested test 2');
+  });
+});
+
+describe('describe block with tests', () => {
+  it('test inside describe', async () => {
+    const stored = testStorage.getStore();
+    assert.strictEqual(stored, 'test inside describe');
+  });
+
+  it('another test inside describe', async () => {
+    const stored = testStorage.getStore();
+    assert.strictEqual(stored, 'another test inside describe');
+  });
+});
+
+test('context is available in async operations within test', async () => {
+  const testName = 'context is available in async operations within test';
+  assert.strictEqual(testStorage.getStore(), testName);
+
+  // Verify context is available in setImmediate
+  const valueInImmediate = await new Promise((resolve) => {
+    setImmediate(() => resolve(testStorage.getStore()));
+  });
+  assert.strictEqual(valueInImmediate, testName);
+
+  // Verify context is available in setTimeout
+  const valueInTimeout = await new Promise((resolve) => {
+    setTimeout(() => resolve(testStorage.getStore()), 0);
+  });
+  assert.strictEqual(valueInTimeout, testName);
+});
+
+test('error events fire for failing tests in fixture', async () => {
+  // Run the fixture test that intentionally fails
+  const fixturePath = join(__dirname, '../fixtures/test-runner/diagnostics-channel-error-test.js');
+  const result = spawnSync(process.execPath, [fixturePath], { encoding: 'utf8' });
+
+  // The fixture test intentionally fails, so exit code should be non-zero
+  assert.notStrictEqual(result.status, 0);
+
+  // Extract and verify error events from fixture output
+  // The fixture outputs JSON with errorEvents array on exit
+  const lines = result.stdout.split('\n');
+  const eventLine = lines.find((line) => line.includes('errorEvents'));
+  assert.ok(eventLine, 'Expected errorEvents line in fixture output');
+  const { errorEvents } = JSON.parse(eventLine);
+  assert.strictEqual(errorEvents.includes('test that intentionally fails'), true);
+});