test: add Worker + --prof regression test

Fixes: #24016

PR-URL: #26011
Reviewed-By: Benjamin Gruenbaum <[email protected]>
Reviewed-By: Ben Noordhuis <[email protected]>
Reviewed-By: Gireesh Punathil <[email protected]>
Reviewed-By: Joyee Cheung <[email protected]>

test/parallel/test-worker-prof.js

@@ -0,0 +1,41 @@
+'use strict';
+const common = require('../common');
+const tmpdir = require('../common/tmpdir');
+const fs = require('fs');
+const assert = require('assert');
+const { spawnSync } = require('child_process');
+const { Worker } = require('worker_threads');
+
+if (!common.isMainThread)
+  common.skip('process.chdir is not available in Workers');
+
+// Test that --prof also tracks Worker threads.
+// Refs: https://github.com/nodejs/node/issues/24016
+
+if (process.argv[2] === 'child') {
+  const spin = `
+  const start = Date.now();
+  while (Date.now() - start < 200);
+  `;
+  new Worker(spin, { eval: true });
+  eval(spin);
+  return;
+}
+
+tmpdir.refresh();
+process.chdir(tmpdir.path);
+spawnSync(process.execPath, ['--prof', __filename, 'child']);
+const logfiles = fs.readdirSync('.').filter((name) => /\.log$/.test(name));
+assert.strictEqual(logfiles.length, 2);  // Parent thread + child thread.
+
+for (const logfile of logfiles) {
+  const lines = fs.readFileSync(logfile, 'utf8').split('\n');
+  const ticks = lines.filter((line) => /^tick,/.test(line)).length;
+
+  // Test that at least 20 ticks have been recorded for both parent and child
+  // threads. When not tracking Worker threads, only 1 or 2 ticks would
+  // have been recorded.
+  // When running locally on x64 Linux, this number is usually at least 150
+  // for both threads, so 15 seems like a very safe threshold.
+  assert(ticks >= 15, `${ticks} >= 15`);
+}