Resolving 'AppComponent › should create the app'

gistfile1.txt

// After runing tests this error occur:
// Template parse errors:
//    'app-main-page' is not a known element:
//    1. If 'app-main-page' is an Angular component, then verify that it is part of this module.
//    2. If 'app-main-page' is a Web Component then add 'CUSTOM_ELEMENTS_SCHEMA' to the '@NgModule.schemas' of this component to suppress this message. (

// Solution below
// Code from: 'app.component.spec.ts'

import { TestBed, async } from '@angular/core/testing';
import { AppComponent } from './app.component';
import { MainPageComponent } from './main-page/main-page.component';

describe('AppComponent', () => {
  beforeEach(async(() => {
    TestBed.configureTestingModule({
    // The code failed at this point because there should been
    // 'MainPageComponent' added to 'declarations'
      declarations: [AppComponent, MainPageComponent]
    }).compileComponents();
  }));
  it('should create the app', async(() => {
    const fixture = TestBed.createComponent(AppComponent);
    const app = fixture.debugElement.componentInstance;
    expect(app).toBeTruthy();
  }));
});