使用 karma jasmine 使用路由器 navigateByUrl 对 function 进行单元测试

Question

I am trying to unit test the following function which has router navigateByUrl, but couldnt execute.then block

.ts code:

back(){ 

    this.router.navigateByUrl('/routepath').then(() => {

         Object.keys(['column']).forEach((obj, val) => {
            myService.setDefaultGroup();
         });

    });
}

Here is what i have tried in my spec.ts

class MockRouter {
   navigateByUrl = () => {
    return {
      then: () => {}
     }
   }
}

configureTestSuite(() => {
    TestBed.configureTestingModule({
       providers: [{ provide: Router, useClass: MockRouter } ]
    })
});

describe('should call back', () => {
    it('should call Router.navigateByUrl', inject([Router], (router: Router) => {
        const spy = spyOn(router, 'navigateByUrl');
        component.back();
    }));
});

What is the output received

TypeError: Cannot read property 'then' of undefined

Expected:

Test case should execute

I am using karma and jasmine to unit test this. Help me out if i am missing anything

Answer 1

When you spyOn a method, it stubs it out to return undefined.

You need to use .and.callThrough() to not lose implementation details.

Try:

describe('should call back', () => {
    it('should call Router.navigateByUrl', inject([Router], (router: Router) => {
        const spy = spyOn(router, 'navigateByUrl').and.callThrough();
        component.back();
    }));
});