Unit testing with default Angular installation

Unit testing with default Angular installation

Asserting that a value is equal to something

expect(someVariable).toEqual('something');

Asserting that a value is defined

expect(someVariable).toBeDefined();

Asserting that a value is true

expect(someVariable).toBeTruthy();

Asserting that a value is false

expect(someVariable).toBeFalsy();

Getting instance of a service

let mockedService = TestBed.get(YourService);

Simple test structure

  it('should be created', () => {
    expect(component).toBeTruthy();
  });

Injecting a service into a test

  it('your test', inject([YourService], (service: YourService) => {
 
  }));

Asserting that some method is called

let spySomeMethod = spyOn(someInstance, 'someMethod');
 
// do something here
 
expect(spySomeMethod).toHaveBeenCalled();

Asserting that some method is called with given arguments

let spySomeMethod = spyOn(someInstance, 'someMethod').and.callFake((arg1, arg2) => {
  expect(arg1).toEqual(10);
  expect(arg2).toEqual(20);
});
 
// do something here
 
expect(spySomeMethod).toHaveBeenCalled();

Mocked Http Requests

1) Instead of using HttpClientModule, you should use HttpClientTestingModule. You will also use HttpTestingController. Below how to import and configure them:

...
import { HttpClientTestingModule, HttpTestingController } from "@angular/common/http/testing";
...
 
describe('YourClass', () => {
 
  beforeEach(() => {
    TestBed.configureTestingModule({
      imports:
        ...
        [ AppRoutingModule, HttpClientTestingModule ]
        ...
    });
  });
  ...
});

2) In your test you need to get an instance of HttpTestingController:

  ...
  it('your test', () => {
 
    let httpMock = TestBed.get(HttpTestingController);
 
  });
  ...

3) In the same test you should assert that a call has been made with:

    let mockedResponse = {
        statusCode: 200,
        body: {
            anything: 'your endpoint returns'
        }
    }
 
    const request = httpMock.expectOne('http://some.request.url/to/somewhere');
 
    request.flush(mockedResponse);
    httpMock.verify();

Expecting that a method is called X times

    let spySomeMethod = spyOn(someInstance, 'someMethod');
 
    // do something here
 
    expect(spySomeMethod.calls.count()).toEqual(2);

Executing code prior to each test

  beforeEach(() => {
    // do your code here
  });

Dependencies configuration

describe('YourComponent', () => {
  let component: YourComponent;
  let fixture: ComponentFixture<YourComponent>;
 
  beforeEach(async(() => {
    TestBed.configureTestingModule({
      declarations:
        [  ],
      imports:
        [  ],
      providers:
        [  ]
    })
    .compileComponents();
  }));
 
  beforeEach(() => {
    fixture = TestBed.createComponent(YourComponent);
    component = fixture.componentInstance;
    fixture.detectChanges();
  });
  ...
})

Testing if a html tag and content exists

  it('should render title in a h1 tag', async(() => {
    const fixture = TestBed.createComponent(AppComponent);
    fixture.detectChanges();
    const compiled = fixture.debugElement.nativeElement;
    expect(compiled.querySelector('h1').textContent).toContain('Website title');
  }));