test-sub-component.js

import { MockComponent } from 'ng2-mock-component';
import { By } from '@angular/platform-browser';

describe('ImgGalleryComponent', () => {
  beforeEach(async(() => {
    TestBed.configureTestingModule({
      declarations: [
        ImgGalleryComponent,
        MockComponent({selector: 'app-img-carousel', inputs: ['images', 'currentSlide', 'isFullscreen']})
      ]
    })
    .compileComponents();
  }));

  // ... more setup 

  it('should contain a carousel', () => {
    const carousel = fixture.debugElement.query(By.css('app-img-carousel'))
    expect(carousel).toBeTruthy();

    const carouselComponent = carousel.componentInstance;
    expect(carouselComponent.isFullscreen).toBe(true);
    expect(carouselComponent.images.length).toBe(3);
    expect(carouselComponent.currentSlide).toBe(0);
  });
});