Zoneless

If your Angular app is zoneless, use the async/await approach for your tests.

Zoneless apps should prefer runTasksUntilStableAsync and predefinedHttpCallInstructionsAsync. The fakeAsync / tick() approach is designed for zone-based tests and is not the right fit for zoneless apps.

What to use

• Use async test functions.
• Use runTasksUntilStableAsync.
• Use predefinedHttpCallInstructionsAsync for HTTP mocking.
• Pass advanceTimers if your test environment uses fake timers.

Why this matters

Zoneless Angular does not rely on Zone.js to decide when a component is stable. That makes the async/await stabilization flow the most reliable option for tests that should match zoneless runtime behavior.

Example

it('should stabilize in a zoneless app', async () => {
  await runTasksUntilStableAsync(fixture, {
    httpCallInstructions: [
      predefinedHttpCallInstructionsAsync.get.success('/api/items', () => items),
    ],
  });
});

Troubleshooting: delayed work should affect stability

Sometimes an app schedules work with setTimeout, setInterval, or another delayed callback before the first HTTP request exists.

If that delayed work should keep the app unstable until it finishes, wrap it with Angular's PendingTasks.

This works best for application code you control. If the timer lives inside a third-party library and you cannot realistically wrap it with PendingTasks, the usual solution is to mock that library or the code path that triggers it in your test.

Example:

import {inject, PendingTasks} from '@angular/core';

const pendingTasks = inject(PendingTasks);
const taskCleanup = pendingTasks.add();

setTimeout(() => {
  try {
    // do delayed work that should keep the test unstable
  } finally {
    taskCleanup();
  }
}, 300);

Without PendingTasks, Angular may consider the fixture stable before that delayed work produces a request or state change.