.

test/es-module/test-esm-initialization.mjs

@@ -1,30 +1,31 @@
 import '../common/index.mjs';
 import * as fixtures from '../common/fixtures.mjs';
 import assert from 'node:assert';
-import { spawnSync } from 'node:child_process';
+import { execPath } from 'node:process';
+import { describe, it } from 'node:test';
 
+import spawn from './helper.spawnAsPromised.mjs';
 
-{ // Verify unadulterated source is loaded when there are no loaders
-  const { status, stderr, stdout } = spawnSync(
-    process.execPath,
-    [
+
+describe('ESM: ensure initialisation happens only once', { concurrency: true }, () => {
+  it(async () => {
+    const { code, stderr, stdout } = await spawn(execPath, [
       '--loader',
       fixtures.fileURL('es-module-loaders', 'loader-resolve-passthru.mjs'),
       '--no-warnings',
       fixtures.path('es-modules', 'runmain.mjs'),
-    ],
-    { encoding: 'utf8' },
-  );
+    ]);
 
-  // Length minus 1 because the first match is the needle.
-  const resolveHookRunCount = (stdout.match(/resolve passthru/g)?.length ?? 0) - 1;
+    // Length minus 1 because the first match is the needle.
+    const resolveHookRunCount = (stdout.match(/resolve passthru/g)?.length ?? 0) - 1;
 
-  assert.strictEqual(stderr, '');
-  /**
-   * resolveHookRunCount = 2:
-   * 1. fixtures/…/runmain.mjs
-   * 2. node:module (imported by fixtures/…/runmain.mjs)
-   */
-  assert.strictEqual(resolveHookRunCount, 2);
-  assert.strictEqual(status, 0);
-}
+    assert.strictEqual(stderr, '');
+    /**
+     * resolveHookRunCount = 2:
+     * 1. fixtures/…/runmain.mjs
+     * 2. node:module (imported by fixtures/…/runmain.mjs)
+     */
+    assert.strictEqual(resolveHookRunCount, 2);
+    assert.strictEqual(code, 0);
+  });
+});