Function testRunnerWatch

test/common/watch.js:72–230

({
  fileToUpdate,
  file,
  action = 'update',
  fileToCreate,
  isolation,
  useRunApi = false,
  cwd = tmpdir.path,
  runnerCwd,
})

}

async function testRunnerWatch({
  fileToUpdate,
  file,
  action = 'update',
  fileToCreate,
  isolation,
  useRunApi = false,
  cwd = tmpdir.path,
  runnerCwd,
}) {
  const ran1 = Promise.withResolvers();
  const ran2 = Promise.withResolvers();

  let args;
  if (useRunApi) {
    // Use the fixture that calls run() API
    const runner = fixtures.path('test-runner-watch.mjs');
    args = [runner];
    if (file) args.push('--file', file);
    if (runnerCwd) args.push('--cwd', runnerCwd);
    if (isolation) args.push('--isolation', isolation);
  } else {
    // Use CLI --watch --test flags
    args = ['--watch', '--test', '--test-reporter=spec',
            isolation ? `--test-isolation=${isolation}` : '',
            file ? fixturePaths[file] : undefined].filter(Boolean);
  }

  const child = spawn(process.execPath, args,
                      { encoding: 'utf8', stdio: 'pipe', cwd });
  let stdout = '';
  let currentRun = '';
  const runs = [];

  child.stdout.on('data', (data) => {
    stdout += data.toString();
    currentRun += data.toString();
    const testRuns = stdout.match(/^\S+ duration_ms\s\d+/gm);
    if (testRuns?.length >= 1) ran1.resolve();
    if (testRuns?.length >= 2) ran2.resolve();
  });

  const testUpdate = async () => {
    await ran1.promise;
    runs.push(currentRun);
    currentRun = '';
    const content = fixtureContent[fileToUpdate];
    const path = fixturePaths[fileToUpdate];

    await performFileOperation(
      () => writeFileSync(path, content),
      useRunApi,
    );
    await ran2.promise;

    runs.push(currentRun);
    child.kill();
    await once(child, 'exit');