Repository: nodejs/node
Pull request: test_runner: run single test file benchmark

With reference to #55723:

As I'm exploring the possibility of adding a new kind of isolation (worker thread), I think we should add at least one benchmark to measure the differences in overhead between various isolation methods.  
For example, I would expect a worker thread to have less computational overhead than a process.  
This benchmark is meant to trace and highlight these kinds of differences

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Changed files:
filename: benchmark/test_runner/run-single-test-file.js
patch: @@ -0,0 +1,62 @@
+'use strict';
+const common = require('../common');
+
+const tmpdir = require('../../test/common/tmpdir');
+const { run } = require('node:test');
+const { writeFileSync, mkdirSync } = require('node:fs');
+const { join } = require('node:path');
+
+const fixtureContent = "const test = require('node:test'); test('test has ran');";
+
+function makeTestDirWithFiles(dirPath, count) {
+  mkdirSync(dirPath);
+  for (let i = 0; i < count; i++) {
+    writeFileSync(join(dirPath, `test-${i}.js`), fixtureContent);
+  }
+}
+
+function getTestDirPath(numberOfTestFiles) {
+  return join(tmpdir.path, `${numberOfTestFiles}-tests`);
+}
+
+function setup(numberOfTestFiles) {
+  tmpdir.refresh();
+  const dirPath = getTestDirPath(numberOfTestFiles);
+  makeTestDirWithFiles(dirPath, numberOfTestFiles);
+}
+
+/**
+ * This benchmark evaluates the overhead of running a single test file under different
+ * isolation modes.
+ * Specifically, it compares the performance of running tests in the
+ * same process versus creating multiple processes.
+ */
+const bench = common.createBenchmark(main, {
+  numberOfTestFiles: [1, 10, 100],
+  isolation: ['none', 'process'],
+}, {
+  // We don't want to test the reporter here
+  flags: ['--test-reporter=./benchmark/fixtures/empty-test-reporter.js'],
+});
+
+async function runBenchmark({ numberOfTestFiles, isolation }) {
+  const dirPath = getTestDirPath(numberOfTestFiles);
+  const stream = run({
+    cwd: dirPath,
+    isolation,
+    concurrency: false, // We don't want to run tests concurrently
+  });
+
+  // eslint-disable-next-line no-unused-vars
+  for await (const _ of stream);
+
+  return numberOfTestFiles;
+}
+
+function main(params) {
+  setup(params.numberOfTestFiles);
+  bench.start();
+  runBenchmark(params).then(() => {
+    bench.end(1);
+  });
+}