Illegal state: Could not load the summary for directive AppComponent

Question

I am writing a spec.ts file in angular and getting the following error:

Failed: Illegal state: Could not load the summary for directive AppComponent.

Below is the code I tried

import { TestBed, async } from "@angular/core/testing";
    import { AppComponent } from "./app.component";

    describe('AppComponent', () => {
        beforeEach(() => {
            TestBed.configureTestingModule({
                declarations: [
                    AppComponent
                ],
            });
        });
    });

    it('should create the app', async(() => {
        let fixture = TestBed.createComponent(AppComponent);
        let app = fixture.debugElement.componentInstance;
        expect(app).toBeTruthy();
    }));``

Answer 1

It seems that you're using a component which includes another components inside. You have to add all the components that you used in AppComponent in declaration of configureTestingModule