Jasmine Unit Test Abstract class

Question

Is there a way to create a jasmine unit test for an abstract component?

doing

const fixture = TestBed.createComponent(MyAbstractComponent);

says, "cannot assign an abstract constructor type to a non-abstract constructor type"

I tried some searching but nothing comes up.

Answer 1

You can create a simple class in your test file which extends from abstract class (do not forget to mock abstract methods), than just test its non abstract methods. Let's say we have MyAbstractClass :

export abstract class MyAbstractClass {
  sum(a: number, b: number): number {
    return a + b;
  }

  abstract calc1(): void;
  abstract calc2(): void;
}

and then in spec file we can just create a new derived class:

class MyClass extends MyAbstractClass {
  // just mock any abstract method
  calc1(): void {
    return;
  }
  calc2(): void {
    return;
  }
}

So now we can write tests for non-abstract methods:

describe('MyAbstractClass', () => {
  let myClass: MyClass;
  beforeEach(() => {
    myClass = new MyClass();
  });

  it('sum two args', () => {
    const a = 1, b = 2;

    const sum = myClass.sum(a, b);

    expect(sum).toBe(3);
  });
});

Also created a stackblitz example of this test example.

Answer 2

Here is what I did to test an angular pipe SafePipe that was using a built in abstract class DomSanitizer .

 // 1. Import the pipe/component to be tested import { SafePipe } from './safe.pipe'; // 2. Import the abstract class import { DomSanitizer } from '@angular/platform-browser'; // 3. Important step - create a mock class which extends // from the base class imported above and add implement // the mock methods class MockDomSanitizer extends DomSanitizer { sanitize(): string{ return 'ANY'; } bypassSecurityTrustHtml(): string{ return 'ANY' } bypassSecurityTrustStyle(): string{ return 'ANY' } bypassSecurityTrustScript(): string{ return 'ANY' } bypassSecurityTrustUrl(): string{ return 'ANY' } bypassSecurityTrustResourceUrl(): string{ return 'ANY' } } describe('SafePipe', () => { it('should return an HTML string', () => { // 4. create an instance of pipe class and inject the mocked class above let safePipe = new SafePipe(new MockDomSanitizer()); // 5. Add your asserions as ususal expect(safePipe.transform(null, 'html')).toBeTruthy(); expect(safePipe.transform(null, 'style')).toBeTruthy(); expect(safePipe.transform(null, 'script')).toBeTruthy(); expect(safePipe.transform(null, 'url')).toBeTruthy(); expect(safePipe.transform(null, 'resourceUrl')).toBeTruthy(); expect(safePipe.transform(null, 'anything')).toContain('anything'); }); });