test_runner: run top level tests in a microtask

lib/internal/test_runner/harness.js

@@ -25,6 +25,7 @@ const {
  setupTestReporters,
  shouldColorizeTestFiles,
 } = require('internal/test_runner/utils');
+const { queueMicrotask } = require('internal/process/task_queues');
 const { bigint: hrtime } = process.hrtime;
 
 const testResources = new SafeMap();
@@ -181,6 +182,7 @@ function setup(root) {
 
  root.harness = {
  __proto__: null,
+ allowTestsToRun: false,
  bootstrapComplete: false,
  coverage: FunctionPrototypeBind(collectCoverage, null, root, coverage),
  counters: {
@@ -219,7 +221,16 @@ function getGlobalRoot() {
 
 async function startSubtest(subtest) {
  await reportersSetup;
- getGlobalRoot().harness.bootstrapComplete = true;
+
+ const root = getGlobalRoot();
+ if (!root.harness.bootstrapComplete) {
+ root.harness.bootstrapComplete = true;
+ queueMicrotask(() => {
+ root.harness.allowTestsToRun = true;
+ root.processPendingSubtests();
+ });
+ }
+
  await subtest.start();
 }
 

lib/internal/test_runner/runner.js

@@ -538,6 +538,7 @@ function run(options = kEmptyObject) {
  }
  const runFiles = () => {
  root.harness.bootstrapComplete = true;
+ root.harness.allowTestsToRun = true;
  return SafePromiseAllSettledReturnVoid(testFiles, (path) => {
  const subtest = runTestFile(path, filesWatcher, opts);
  filesWatcher?.runningSubtests.set(path, subtest);

lib/internal/test_runner/test.js

@@ -603,7 +603,7 @@ class Test extends AsyncResource {
  // it. Otherwise, return a Promise to the caller and mark the test as
  // pending for later execution.
  this.reporter.enqueue(this.nesting, this.loc, this.name);
- if (!this.parent.hasConcurrency()) {
+ if (!this.root.harness.allowTestsToRun || !this.parent.hasConcurrency()) {
  const deferred = createDeferredPromise();
 
  deferred.test = this;

test/fixtures/test-runner/output/source_mapped_locations.snapshot

@@ -21,6 +21,9 @@ not ok 1 - fails
  *
  *
  *
+ *
+ *
+ *
  ...
 1..1
 # tests 1