test_runner: publish to TracingChannel node.test for OTel instrumentation by MoLow · Pull Request #62502 · nodejs/node

MoLow · 2026-03-30T10:54:04Z

No description provided.

nodejs-github-bot · 2026-03-30T10:54:11Z

Review requested:

@nodejs/test_runner

benjamingr

really cool

Copilot

Pull request overview

Adds diagnostics channel tracing hooks to the built-in Node.js test runner to enable OpenTelemetry-style instrumentation via diagnostics_channel.tracingChannel('node.test').

Changes:

Introduce a shared TracingChannel('node.test') for the internal test runner and export it from test-runner utils.
Wrap test/suite execution with start.runStores(...) and publish end/error lifecycle events.
Add documentation and new tests/fixtures validating lifecycle events and AsyncLocalStorage propagation via bindStore().

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
test/parallel/test-runner-diagnostics-channel.js	New parallel test covering start/end/error events and `bindStore` propagation.
test/fixtures/test-runner/diagnostics-channel-error-test.js	Fixture that intentionally fails to validate `error` event emission.
lib/internal/test_runner/utils.js	Creates and exports `testChannel` via `diagnostics_channel.tracingChannel('node.test')`.
lib/internal/test_runner/test.js	Instruments `Test.run()` and `Suite.createBuild()` to emit tracing lifecycle events and run stores.
doc/api/test.md	Documents the new tracing channels and provides an OpenTelemetry integration example.

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doc/api/test.md

Copilot · 2026-03-30T11:01:29Z

doc/api/test.md

+import { diagnosticsChannel } from 'node:diagnostics_channel';
+import { AsyncLocalStorage } from 'node:async_hooks';
+import { context, trace } from '@opentelemetry/api';
+
+const testStorage = new AsyncLocalStorage();
+const testChannel = diagnosticsChannel.tracingChannel('node.test');
+const tracer = trace.getTracer('test-tracer');


The OpenTelemetry example imports diagnosticsChannel from node:diagnostics_channel, but that module's public API exports functions like tracingChannel (and does not export a diagnosticsChannel binding). As written, the example code will throw at import time / diagnosticsChannel.tracingChannel(...) will be undefined. Update the example to use the actual node:diagnostics_channel exports (e.g., import tracingChannel directly or import the module namespace and call .tracingChannel).

Copilot · 2026-03-30T11:01:29Z

lib/internal/test_runner/test.js

+      if (channelContext !== null && testChannel.end.hasSubscribers) {
+        testChannel.end.publish(channelContext);
+      }
    } catch (err) {
+      if (channelContext !== null && testChannel.error.hasSubscribers) {
+        testChannel.error.publish({ __proto__: null, ...channelContext, error: err });
+      }
      this.fail(new ERR_TEST_FAILURE(err, kTestCodeFailure));
    }


In Suite.createBuild(), the tracing:node.test:end event is only published on the success path. If the suite function throws, tracing:node.test:error is published but end is never emitted, which makes lifecycle instrumentation incomplete/inconsistent with Test.run() (where end is always emitted in finally). Consider publishing end in a finally block so it fires for both success and error cases.

Copilot · 2026-03-30T11:01:30Z

lib/internal/test_runner/test.js

+      let suiteFn = this.fn;
+      if (channelContext !== null && testChannel.start.hasSubscribers) {
+        suiteFn = (...fnArgs) => testChannel.start.runStores(channelContext,
+                                                             () => ReflectApply(this.fn, this, fnArgs),
+        );


The wrapped suiteFn calls ReflectApply(this.fn, ...), but Suite mutates this.fn to noop in the constructor after kicking off createBuild(). This makes the wrapper fragile and easy to break if execution order changes. Prefer invoking the originally captured suite function (e.g., via a local baseFn) inside the wrapper instead of referencing this.fn.

atlowChemi · 2026-03-30T11:03:20Z

doc/api/test.md

+* `data` {Object}
+  * `name` {string} The name of the test.
+  * `nesting` {number} The nesting level of the test.
+  * `file` {string} The path to the test file.


in most places we also say something around the lines of "or undefined when in REPL", I think the 3 occurrences here should too?

atlowChemi · 2026-03-30T11:04:49Z

doc/api/test.md

+```mjs
+import { diagnosticsChannel } from 'node:diagnostics_channel';
+import { AsyncLocalStorage } from 'node:async_hooks';
+import { context, trace } from '@opentelemetry/api';


Is it common/customary for the node docs to show examples with external libraries?

atlowChemi · 2026-03-30T11:16:19Z

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

+test('bindStore propagates into test body via start channel', async () => {
+  const expectedName = 'bindStore propagates into test body via start channel';


why not:

Suggested change

test('bindStore propagates into test body via start channel', async () => {

const expectedName = 'bindStore propagates into test body via start channel';

const expectedName = 'bindStore propagates into test body via start channel';

test(expectedName, async () => {

atlowChemi · 2026-03-30T11:17:09Z

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

+  });
+});
+
+const { describe, it } = require('node:test');


Any reason for this to be down here and not alongside the test in line 5?

codecov · 2026-03-30T12:32:05Z

Codecov Report

❌ Patch coverage is 95.52239% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 89.70%. Comparing base (d9645d7) to head (75fe3a3).
⚠️ Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
lib/internal/test_runner/test.js	95.31%	3 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main   #62502   +/-   ##
=======================================
  Coverage   89.69%   89.70%           
=======================================
  Files         692      692           
  Lines      214039   214104   +65     
  Branches    41064    41078   +14     
=======================================
+ Hits       191985   192062   +77     
  Misses      14134    14134           
+ Partials     7920     7908   -12

Files with missing lines	Coverage Δ
lib/internal/test_runner/utils.js	`62.36% <100.00%> (+0.17%)`	⬆️
lib/internal/test_runner/test.js	`96.74% <95.31%> (-0.06%)`	⬇️

... and 32 files with indirect coverage changes

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MoLow requested a review from Copilot March 30, 2026 10:54

nodejs-github-bot added needs-ci PRs that need a full CI run. test_runner Issues and PRs related to the test runner subsystem. labels Mar 30, 2026

Copilot started reviewing on behalf of MoLow March 30, 2026 10:55 View session

benjamingr approved these changes Mar 30, 2026

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Copilot AI reviewed Mar 30, 2026

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atlowChemi reviewed Mar 30, 2026

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test_runner: publish to TracingChannel node.test for instrumentation

75fe3a3

MoLow force-pushed the test-tracing-channel branch from c3b10e5 to 75fe3a3 Compare March 30, 2026 11:08

atlowChemi reviewed Mar 30, 2026

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test_runner: publish to TracingChannel node.test for OTel instrumentation#62502

test_runner: publish to TracingChannel node.test for OTel instrumentation#62502
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		test('bindStore propagates into test body via start channel', async () => {
		const expectedName = 'bindStore propagates into test body via start channel';

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