test_runner: emit event when file changes in watch mode

PR-URL: #57903 Reviewed-By: Pietro Marchini <pietro.marchini94@gmail.com> Reviewed-By: Jake Yuesong Li <jake.yuesong@gmail.com>

Author: JacopoPatroclo

doc/api/test.md

@@ -1121,6 +1121,9 @@ const customReporter = new Transform({
  case 'test:watch:drained':
  callback(null, 'test watch queue drained');
  break;
+ case 'test:watch:restarted':
+ callback(null, 'test watch restarted due to file change');
+ break;
  case 'test:start':
  callback(null, `test ${event.data.name} started`);
  break;
@@ -1166,6 +1169,9 @@ const customReporter = new Transform({
  case 'test:watch:drained':
  callback(null, 'test watch queue drained');
  break;
+ case 'test:watch:restarted':
+ callback(null, 'test watch restarted due to file change');
+ break;
  case 'test:start':
  callback(null, `test ${event.data.name} started`);
  break;
@@ -1210,6 +1216,9 @@ export default async function * customReporter(source) {
  case 'test:watch:drained':
  yield 'test watch queue drained\n';
  break;
+ case 'test:watch:restarted':
+ yield 'test watch restarted due to file change\n';
+ break;
  case 'test:start':
  yield `test ${event.data.name} started\n`;
  break;
@@ -1250,6 +1259,9 @@ module.exports = async function * customReporter(source) {
  case 'test:watch:drained':
  yield 'test watch queue drained\n';
  break;
+ case 'test:watch:restarted':
+ yield 'test watch restarted due to file change\n';
+ break;
  case 'test:start':
  yield `test ${event.data.name} started\n`;
  break;
@@ -3175,6 +3187,10 @@ generated for each test file in addition to a final cumulative summary.
 
 Emitted when no more tests are queued for execution in watch mode.
 
+### Event: `'test:watch:restarted'`
+
+Emitted when one or more tests are restarted due to a file change in watch mode.
+
 ## Class: `TestContext`
 
 <!-- YAML

lib/internal/test_runner/runner.js

@@ -481,6 +481,7 @@ function watchFiles(testFiles, opts) {
  // Reset the topLevel counter
  opts.root.harness.counters.topLevel = 0;
  }
+
  await runningSubtests.get(file);
  runningSubtests.set(file, runTestFile(file, filesWatcher, opts));
  }
@@ -508,6 +509,8 @@ function watchFiles(testFiles, opts) {
  // Reset the root start time to recalculate the duration
  // of the run
  opts.root.clearExecutionTime();
+ opts.root.reporter[kEmitMessage]('test:watch:restarted');
+
  // Restart test files
  if (opts.isolation === 'none') {
  PromisePrototypeThen(restartTestFile(kIsolatedProcessName), undefined, (error) => {

test/parallel/test-runner-run-watch.mjs

@@ -257,6 +257,56 @@ describe('test runner watch mode', () => {
  assert.notDeepStrictEqual(durations[0][1], durations[1][1]);
  });
 
+ it('should emit test:watch:restarted when file is updated', async () => {
+ let alreadyDrained = false;
+ const events = [];
+ const testWatchRestarted = common.mustCall(1);
+
+ const controller = new AbortController();
+ const stream = run({
+ cwd: tmpdir.path,
+ watch: true,
+ signal: controller.signal,
+ }).on('data', function({ type }) {
+ events.push(type);
+ if (type === 'test:watch:restarted') {
+ testWatchRestarted();
+ }
+ if (type === 'test:watch:drained') {
+ if (alreadyDrained) {
+ controller.abort();
+ }
+ alreadyDrained = true;
+ }
+ });
+
+ await once(stream, 'test:watch:drained');
+
+ writeFileSync(join(tmpdir.path, 'test.js'), fixtureContent['test.js']);
+
+ // eslint-disable-next-line no-unused-vars
+ for await (const _ of stream);
+
+ assert.partialDeepStrictEqual(events, [
+ 'test:watch:drained',
+ 'test:watch:restarted',
+ 'test:watch:drained',
+ ]);
+ });
+
+ it('should not emit test:watch:restarted since watch mode is disabled', async () => {
+ const stream = run({
+ cwd: tmpdir.path,
+ watch: false,
+ });
+
+ stream.on('test:watch:restarted', common.mustNotCall());
+ writeFileSync(join(tmpdir.path, 'test.js'), fixtureContent['test.js']);
+
+ // eslint-disable-next-line no-unused-vars
+ for await (const _ of stream);
+ });
+
  describe('test runner watch mode with different cwd', () => {
  it(
  'should execute run using a different cwd for the runner than the process cwd',