test_runner: sync ESM exports when mocking timers

This change ensures that ESM imports of node:timers/promises are correctly
mocked when using mock.timers.enable(). This is achieved by calling
syncBuiltinESMExports() whenever the mocked timers are toggled or reset.

Fixes: #62081

Author: Siddhartha-singh01

lib/internal/test_runner/mock/mock_timers.js

@@ -24,6 +24,7 @@ const {
   validateNumber,
   validateStringArray,
 } = require('internal/validators');
+const { syncBuiltinESMExports } = require('internal/modules/cjs/loader');
 
 const {
   AbortError,
@@ -440,9 +441,9 @@ class MockTimers {
 
     const eventIt = EventEmitter.on(emitter, 'data');
     const timer = this.#createTimer(true,
-                                    () => emitter.emit('data'),
-                                    interval,
-                                    options);
+      () => emitter.emit('data'),
+      interval,
+      options);
 
     try {
       // eslint-disable-next-line no-unused-vars
@@ -628,6 +629,7 @@ class MockTimers {
     const target = activate ? options.toFake : options.toReal;
     ArrayPrototypeForEach(this.#timersInContext, (timer) => target[timer]());
     this.#isEnabled = activate;
+    syncBuiltinESMExports();
   }
 
   /**

test/parallel/test-runner-mock-timers-esm.mjs

@@ -0,0 +1,44 @@
+import { describe, it } from 'node:test';
+import { setTimeout } from 'node:timers/promises';
+import assert from 'node:assert';
+
+describe('Mock Timers ESM Regression', () => {
+    it('should work with node:timers/promises and runAll() in ESM', async (t) => {
+        t.mock.timers.enable({ apis: ['Date', 'setTimeout'] });
+        const startTime = Date.now();
+        let t1 = 0;
+
+        await Promise.all([
+            (async () => {
+                await setTimeout(1000);
+                t1 = Date.now();
+            })(),
+            (async () => {
+                // Wait for the next tick to ensure setTimeout has been called
+                await new Promise(resolve => process.nextTick(resolve));
+                t.mock.timers.runAll();
+            })()
+        ]);
+
+        assert.strictEqual(t1 - startTime, 1000);
+    });
+
+    it('should work with node:timers/promises and tick() in ESM', async (t) => {
+        t.mock.timers.enable({ apis: ['Date', 'setTimeout'] });
+        const startTime = Date.now();
+        let t1 = 0;
+
+        await Promise.all([
+            (async () => {
+                await setTimeout(500);
+                t1 = Date.now();
+            })(),
+            (async () => {
+                await new Promise(resolve => process.nextTick(resolve));
+                t.mock.timers.tick(500);
+            })()
+        ]);
+
+        assert.strictEqual(t1 - startTime, 500);
+    });
+});