In Angular, when writing unit tests, it is crucial to handle asynchronous operations properly, especially when dealing with observables like those returned by the subscribe method. If you have a test that includes code within the subscribe block, and it's not running as expected, it might be due to the asynchronous nature of the observable.

To properly test code within a subscribe block, you should use the done function in your test to signal that the asynchronous part of the test has completed. This is necessary because the test framework will not wait for asynchronous operations to complete by default.

Here's an example of how you can structure your test to handle the asynchronous behavior of observables:

import { TestBed, fakeAsync, tick } from '@angular/core/testing'; import { YourService } from './your.service'; describe('YourService', () => { let service: YourService; beforeEach(() => { TestBed.configureTestingModule({ providers: [YourService] }); service = TestBed.inject(YourService); }); it('should do something asynchronously', (done) => { const expectedResult = 'Expected result'; // Call the method that returns an Observable const observable$ = service.someMethod(); // Subscribe to the observable observable$.subscribe((result) => { // Perform your assertions inside the subscribe block expect(result).toBe(expectedResult); // Signal that the asynchronous part of the test has completed done(); }); }); });

In the example above, we are using the done function to signal the completion of the asynchronous part of the test. It's essential to call done() within the subscribe block after performing the necessary assertions to let the test framework know that it should wait for this asynchronous part to complete before considering the test as passed.

Additionally, make sure to handle error scenarios within the subscribe block by using the second callback function for error handling.

If your test still doesn't run as expected, ensure that the observable is emitting values correctly, and there are no issues with the service or its dependencies.

Remember, when dealing with asynchronous code in Angular tests, using fakeAsync and tick is another approach you can consider, which allows you to simulate the passage of time and control the asynchronous operations within the test. However, for observable-based tests, the done function is the most straightforward approach to handle asynchronous behavior.

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