From b451d58e9ad37dbb756f1553cbe35e3337be518c Mon Sep 17 00:00:00 2001
From: Matteo Collina <hello@matteocollina.com>
Date: Tue, 29 Jul 2025 11:44:47 +0200
Subject: [PATCH 1/2] test_runner: make it compatible with fake timers

Signed-off-by: Matteo Collina <hello@matteocollina.com>
---
 lib/internal/test_runner/test.js | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/internal/test_runner/test.js b/lib/internal/test_runner/test.js
index 2203bbd3497659..97d53c097261d7 100644
--- a/lib/internal/test_runner/test.js
+++ b/lib/internal/test_runner/test.js
@@ -149,7 +149,7 @@ function stopTest(timeout, signal) {
 
     disposeFunction = () => {
       abortListener[SymbolDispose]();
-      timer[SymbolDispose]();
+      clearTimeout(timer);
     };
   }
 

From 2779c84ba2f3ba8570414e052250848cc595a8c2 Mon Sep 17 00:00:00 2001
From: Matteo Collina <hello@matteocollina.com>
Date: Wed, 4 Mar 2026 15:59:18 +0100
Subject: [PATCH 2/2] test_runner: add test for fake timers compatibility with
 timeout

Signed-off-by: Matteo Collina <hello@matteocollina.com>
---
 .../test-runner/mock-timers-with-timeout.js   | 43 +++++++++++++++++++
 .../test-runner-mock-timers-with-timeout.js   | 14 ++++++
 2 files changed, 57 insertions(+)
 create mode 100644 test/fixtures/test-runner/mock-timers-with-timeout.js
 create mode 100644 test/parallel/test-runner-mock-timers-with-timeout.js

diff --git a/test/fixtures/test-runner/mock-timers-with-timeout.js b/test/fixtures/test-runner/mock-timers-with-timeout.js
new file mode 100644
index 00000000000000..4eb94ec5d6d8e9
--- /dev/null
+++ b/test/fixtures/test-runner/mock-timers-with-timeout.js
@@ -0,0 +1,43 @@
+'use strict';
+
+// Simulate @sinonjs/fake-timers: patch the timers module BEFORE
+// the test runner is loaded, so the test runner captures the patched
+// versions at import time.
+const nodeTimers = require('node:timers');
+const originalSetTimeout = nodeTimers.setTimeout;
+const originalClearTimeout = nodeTimers.clearTimeout;
+
+const fakeTimers = new Map();
+let nextId = 1;
+
+nodeTimers.setTimeout = (fn, delay, ...args) => {
+  const id = nextId++;
+  const timer = originalSetTimeout(fn, delay, ...args);
+  fakeTimers.set(id, timer);
+  // Sinon fake timers return an object with unref/ref but without
+  // Symbol.dispose, which would cause the test runner to throw.
+  return { id, unref() {}, ref() {} };
+};
+
+nodeTimers.clearTimeout = (id) => {
+  if (id != null && typeof id === 'object') id = id.id;
+  const timer = fakeTimers.get(id);
+  if (timer) {
+    originalClearTimeout(timer);
+    fakeTimers.delete(id);
+  }
+};
+
+// Now load the test runner - it will capture our patched setTimeout/clearTimeout
+const { test } = require('node:test');
+
+test('test with fake timers and timeout', { timeout: 10_000 }, () => {
+  // This test verifies that the test runner works when setTimeout returns
+  // an object without Symbol.dispose (like sinon fake timers).
+  // Previously, the test runner called timer[Symbol.dispose]() which would
+  // throw TypeError on objects returned by fake timer implementations.
+});
+
+// Restore
+nodeTimers.setTimeout = originalSetTimeout;
+nodeTimers.clearTimeout = originalClearTimeout;
diff --git a/test/parallel/test-runner-mock-timers-with-timeout.js b/test/parallel/test-runner-mock-timers-with-timeout.js
new file mode 100644
index 00000000000000..67f266851fe1ed
--- /dev/null
+++ b/test/parallel/test-runner-mock-timers-with-timeout.js
@@ -0,0 +1,14 @@
+'use strict';
+require('../common');
+const fixtures = require('../common/fixtures');
+const assert = require('node:assert');
+const { spawnSync } = require('node:child_process');
+const { test } = require('node:test');
+
+test('mock timers do not break test timeout cleanup', async () => {
+  const fixture = fixtures.path('test-runner', 'mock-timers-with-timeout.js');
+  const cp = spawnSync(process.execPath, ['--test', fixture], {
+    timeout: 30_000,
+  });
+  assert.strictEqual(cp.status, 0, `Test failed:\nstdout: ${cp.stdout}\nstderr: ${cp.stderr}`);
+});