unit-test.md

Unit Test

When the Coverage seems fucked up

Remove SourceMaps

The option --sourcemaps=false or -sm=false can help the debug when an error occur.
Nevertheless it can be responsible for weird coverage report (which make it innacurate).

Remove this option from the ng test command.

Error: 1 timer(s) still in the queue.

To fix it, you must use the fakeAsync syntax with a tick and wait for stable fixture.

it('should do ...', fakeAsync(() => {

  // Do some stuff here
    
  tick(500);
  fixture.whenStable().then(() => {
  
    // Add your expectation here
      
  });
}));

Testing private methods

No, you can't.

Spying private methods call

Use the spyOn<any> syntax and save the Spy in a variable.
The expectation should be directly the Spy.

it('should ...', () => {
  const spy: Spy = spyOn<any>(component, 'privateMethod');
  component.ngOnInit();
  expect(spy).toHaveBeenCalled();
});

How to test an event in a directive

Check out this example where we want to preventDefault() on the event.

@HostListener('click', ['$event'])
public onClick(event: any): void {
  event.preventDefault();
}

To test it, you must create your own directive and event objects.
Then spy on the event's preventDefault() method.
Simulate the HostListener and finally expect the call.

it('should prevent default on event', () => {
  const directive: ExampleDirective = new ExampleDirective();
  const clickEvent: MouseEvent = new MouseEvent('click', null);
  spyOn(clickEvent, 'preventDefault');
  fixture.detectChanges();
  directive.onClick(clickEvent);
  expect(clickEvent.preventDefault).toHaveBeenCalled();
}

How to test .emit()

In this example, we will test that the @Output outputOnClick emit correctly when onClick() is called.

it('should emit', () => {
  let hasSubscribe: boolean = false;
  component.outputOnClick.subscribe(() => hasSubscribe = true);
  component.onClick();
  expect(hasSubscribe).toBe(true);
});

How to test Observable data

Store the observable in a const and then subscribe to it to eval the callback when the next change.

it('should equal...', fakeAsync(() => {
  const observable: Observable<number> = numberService.getNumber();
  observable.subscribe((number: number) => expect(number).toBe(1));
}));

How to test a function which is called multiple times with params

Save the function as a spy and use the calls args to get all the data in one shot.

it('should call the fn with 1 and then 2', () => {
  const fnSpy: Spy = spyOn(service, 'fn');
  expect(fnSpy.calls.allArgs()).toEqual([[1], [2]]);
});

How to test .toHaveBeenCalledWith() when the param is a function

Instead of passing a real function, or even a noop, you can pass a jasmine type.
The solution is then jasmine.any(Function).

it('should call login() with a callback', () => {
  spyOn(loginService, 'login');
  expect(loginService.login).toHaveBeenCalledWith(jasmine.any(Function));
});

How to test the call of an internal method in a service's constructor

Use the prototype of the service.

it('constructor() should call init()', () => {
  spyOn(AdmFwkKeyboardService.prototype, 'init');
  const newService: AdmFwkKeyboardService = new AdmFwkKeyboardService(logService);
  expect(AdmFwkKeyboardService.prototype.init).toHaveBeenCalled();
});