handle http error spec.ts

it('should show error message when request fails', async () => {
  component.userName = 'IAfanasov';

  fixture.debugElement.query(By.css('button')).nativeElement.click();
  const request = httpMock.expectOne('https://api.github.com/users/IAfanasov/starred');
  request.error(null);
  fixture.detectChanges();
  await fixture.whenRenderingDone();

  const alert = fixture.debugElement.query(By.css('.alert-danger'));
  expect(alert).toBeTruthy();
});

it('should hide the error message when request succeeded after failed one fails', async () => {
  component.userName = 'IAfanasov';

  fixture.debugElement.query(By.css('button')).nativeElement.click();
  const requestToFail = httpMock.expectOne('https://api.github.com/users/IAfanasov/starred');
  requestToFail.error(null);
  fixture.debugElement.query(By.css('button')).nativeElement.click();
  const requestToSucceed = httpMock.expectOne('https://api.github.com/users/IAfanasov/starred');
  requestToSucceed.flush([]);
  fixture.detectChanges();
  await fixture.whenRenderingDone();

  const alert = fixture.debugElement.query(By.css('.alert-danger'));
  expect(alert).toBeFalsy();
});