OverrideComponent with TestBed

Question

I have MainComponent that uses ChildComponentA as a @ViewChild. MainComponent is calling a method on ChildComponentA.

I want to write an unit test case mocking ChildComponentA. How can I do this using TestBed (in Angular 2 RC5)?

Before I used to use overrideDirective(MainComponentName, ChildComponentA, MockChildComponentA); Is there an equivalent to this using TestBed?

I tried using

TestBed.overrideComponent(ChildComponentA,{
        set: {
          template: '<div></div>'
        }
      }); 

which just sets the template, but I want to mock the methods in the component as well.

Answer 1

I think in this case you can try and replace the child component with a mock component. Just create a mock component with the same selector and use TestBed to remove the declaration of the real child component and add the declaration to your mock component.

@Component({
  selector: 'child',
  template: '<div></div>'
})
class MockComponent {

}

And in your test do this to use the mock component:

    TestBed.configureTestingModule({
        imports: [MyModule],
        declarations: [ParentComponent, MockComponent]
    });

    TestBed.overrideModule(MyModule, {
        remove: {
            declarations: [ParentComponent, ChildComponent],
            exports: [ParentComponent, ChildComponent]
        }
    });

More details here: https://github.com/angular/angular/issues/10689. Make sure to re-declare the ParentComponent, it does not work otherwise (not sure why).

If you use @ViewChild to get a reference to the child component, you will need to modify it to not use the type of the component, but an id. Use @ViewChild('child') instead of @ViewChild(ChildComponent). See second example from here: http://learnangular2.com/viewChild/