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What is the difference between fakeAsync, tick, and waitForAsync in Angular unit tests?

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01

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Compare asynchronous test utilities in Angular.

testingasync
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fakeAsync runs tests in a special linear zone where time is simulated and controlled via tick(ms). waitForAsync runs tests with real asynchronous processing (e.g., standard timers or HTTP requests) and requires calling fixture.whenStable() to block until promises resolve.

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Comparing fakeAsync and waitForAsync syntax
import { fakeAsync, tick, waitForAsync, TestBed } from '@angular/core/testing';
import { MyAsyncService } from './my-async.service';

it('should test timers synchronously using fakeAsync', fakeAsync(() => {
  let value = false;
  setTimeout(() => { value = true; }, 1000);

  expect(value).toBeFalse();
  tick(1000);
  expect(value).toBeTrue();
}));
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