testing

Testing

What we'll do in this project

• Test Components
• Test Services
• Test Pipes
• Test Directives
• Test integration between them

Development server

Run ng serve.

Testing components

The complexity of the test depends on what the component does, if the components has inputs or outputs, if it displays some values, if it uses a service and so on...

First we set up a Testing Module

let component: HeaderComponent;
let fixture: ComponentFixture<HeaderComponent>;

beforeEach(async () => {
  await TestBed.configureTestingModule({
    imports: [HeaderComponent]
  })
  .compileComponents();

  fixture = TestBed.createComponent(HeaderComponent);
  component = fixture.componentInstance;
  fixture.detectChanges();
});

In this example, we simply import the component to test. Then, we write some test for the functionality of the component.

If your component is dependant you have to add in the imports and providers arrays or mock them.

it('should create', () => {
  expect(component).toBeDefined();
});

it('should contain "header works!"', () => {
  const bannerElement: HTMLElement = fixture.nativeElement;
  expect(bannerElement.textContent).toContain('header works!');
});

Testing Services

In some cases, we can write our service tests without using Angular testing utilities, testing them directly

describe('ValueService', () => {
  let service: ValueService;
  beforeEach(() => {
    service = new ValueService();
  });
  it('#getValue should return a value', () => {
    expect(service.getValue()).toBe('a value');
  });
});

Using the Angular TestBed

let service: AuthService;
beforeEach(() => {
  TestBed.configureTestingModule({providers: [AuthService]});
  ...
});

then

it('should be isLogged default value', () => {
  service = TestBed.inject(AuthService);
  expect(service.logged()).toBeFalsy();
});

Testing functional guard, resolver, interceptor

A resolver function:

export function productDetailResolver(route: ActivatedRouteSnapshot) => {
  const id = route.paramMap.get('id');
  const productService = inject(ProductService);
  return productService.findById(id)
}

In the test you need to use TestBed.runInInjectionContext to run the resolver function in a injection context

TestBed.runInInjectionContext(() => productResolver(resolveParams))

Testing navigation

To test navigation I used this technique

First, created a Router spy

const routerSpy = jasmine.createSpyObj('Router', ['navigate']);

Then, mock the Router using this spy

TestBed.configureTestingModule({
  // Mock Router
  providers: [{
    provide: Router,
    useValue: routerSpy,
  }]
});
service = TestBed.inject(AuthService);

Finally

it('should call the navigate method with the given parameter', () => {      
  service.logIn();
  const navArgs = routerSpy.navigate.calls.first().args[0];
  expect(navArgs).toEqual(["profile"]);
});

Testing Pipes

A Pipe is a class with one method, transform, this manipulates the input value into a transformed output value.

We have a FormatMoneyPipe what format a number:

describe('FormatMoneyPipe', () => {
  const pipe = new FormatMoneyPipe();

  it('create an instance', () => {
    expect(pipe).toBeTruthy();
  });

  it('should tranform the number to format', () => {
    const value = 25.2564

    const result = pipe.transform(value)
    expect(result).toBe('$25.26');
  });
});

In this case the test is simple.

Testing Directives

In Angular we have 3 types of directives, Attribute directive, Structural directive and Component, we already tested Componentes, now for testing the other two types of directives we need a Host component. When testing these Directives, we use a host Component that renders the host element.

For this example, we have a IsFavoriteDirective that change the color if the valor is false or true. In our test we have a HostComponent to test the attribute directive

@Component({
  standalone: true,
  template: `
    <div [isFavorite]="true" data-testid="favorite"></div>
  `,
  imports: [IsFavoriteDirective],
})
class HostComponent {}

the test describe:

describe('IsFavoriteDirective', () => {
  let fixture: ComponentFixture<HostComponent>;
  let myElement: DebugElement;

  beforeEach(async () => {
    await TestBed.configureTestingModule({
      imports: [IsFavoriteDirective, HostComponent],
    }).compileComponents();
  });

  beforeEach(() => {
    fixture = TestBed.createComponent(HostComponent);
    fixture.detectChanges();
    myElement = fixture.debugElement.query(By.directive(IsFavoriteDirective));
  });

  it('should have red color', () => {
    const bgColor = myElement.nativeElement.style.backgroundColor;
    expect(bgColor).toBe('red');
  });
});

Change the test runner

Angular by default comes with Jasmine and Karma for testing but you can use another test runner if you want.

Web test runner

You can use Web Test Runner

npm i -D @web/test-runner

then, in the angular.json in the test section, change the builder

"test": {
-  "builder": "@angular-devkit/build-angular:karma",
+  "builder": "@angular-devkit/build-angular:web-test-runner",
  ...
}

Futher improvements

• Add missing tests
• Add the search functionality