Testing errors in Angular 5 Unit Testing after subscribtion

Question

I have the following function in my Angular 5 controller on which i want to do UnitTesting using karma.

this.search.getFirstSearch().subscribe(data => {
      this.processSchool = data.search3,
        error =><any> this.errorMessage,
        ()=>{
          if(this.errorMessage ===''){
    console.log('abc')
          }else{
            console.log('xxxx')
          }
        }

    });

Unfortunately, I have difficulties testing the function error statement. I tried the following codes, but as far as I see from generated covrage, this part is not covered.

it('should simulate error 1  ', () => {
    fixture.detectChanges();

    const searchService = fixture.debugElement.injector.get(SearchService);
    const mockCall= spyOn(searchService, 'getFirstSearch').and.returnValue(Observable.throw({status: 404}));

    //call method 
    comp.processData();

  });

  it('should simulate error 2  ', () => {

    const searchService = fixture.debugElement.injector.get(SearchService);
    const mockCall= spyOn(searchService, 'getFirstSearch').and.returnValue(Observable.throw({message: ""}));

    //call method 
    comp.processData();
  });



  it('should simulate error 3 ', async(() => { fixture.detectChanges();
    const searchService = fixture.debugElement.injector.get(SearchService);
    let    error404 = {status: 404};
    backend.connections.subscribe((connection: MockConnection) => {
      connection.mockError(error404 as any as Error);
    });

    comp.processData();
  }));


  ////added test

  it('should simulate error 4 ', () => { fixture.detectChanges();

    const searchService = fixture.debugElement.injector.get(SearchService);
    const mockCall= spyOn(searchService, 'getFirstSearch').and.returnValue(
      new ErrorObservable('TwainService test failure'))

    comp.processData();


  });

  it('should simulate error 5', () => { fixture.detectChanges();

    const searchService = fixture.debugElement.injector.get(SearchService);
    const mockCall= spyOn(searchService, 'getFirstSearch').and.returnValue(Observable.throw({message: ""}));

    comp.processData();

  });

From the generated report, the error part is not covered. What am I missing?

Answer 1

您可以尝试使用.and.throwError，如此处和此处所述 。

spyOn(searchService, 'getFirstSearch').and.throwError({status: 404});

Answer 2

Based on what you have, I think that you might have extraneous curly braces wrapping the parameters passed to the subscribe method. The subscribe signature is .subscribe([onNext], [onError], [onCompleted]) . Otherwise you have set up methods that are assigned to no variable and will never run (thus why it is saying that the code is never ran).

this.search.getFirstSearch().subscribe(
  data => this.processSchool = data.search3, // onNext
  error => this.errorMessage = error,  // onError
  () => { // onCompleted
    if(this.errorMessage === '') {
      console.log('abc')
    } else {
      console.log('xxxx')
    }
  }
);