Angular Nebular component testing

//app.component.spec.ts
import { TestBed } from '@angular/core/testing';
import { AppComponent } from './app.component';
import {
  NbLayoutModule,
  NbSidebarModule,
  NbInputModule,
  NbMenuModule,
} from '@nebular/theme';

import { NbThemeService } from '@nebular/theme';
import { RouterTestingModule } from '@angular/router/testing';
import { ThemeModule } from './@theme/theme.module';

describe('AppComponent', () => {
  beforeEach(async () => {
    TestBed.configureTestingModule({
      declarations: [AppComponent],
      imports: [
        RouterTestingModule.withRoutes([]),
        ThemeModule.forRoot(),
        NbLayoutModule,
        NbSidebarModule,
        NbInputModule,
        NbMenuModule,
      ],
      providers: [NbThemeService],
    }).compileComponents();
  });

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