How to use the @nebular/theme.NbThemeModule.forRoot function in @nebular/theme

beforeEach(() => {
    TestBed.configureTestingModule({
      imports: [
        NbThemeModule.forRoot(),
        NbOverlayModule.forRoot(),
        NbLayoutModule,
        PortalModule,
        RouterTestingModule.withRoutes([]),
      ],
    });

    // Have to create layout component as it's required for scroll service to work properly.
    // Also it registers overlay container so we don't have to create it manually.
    TestBed.createComponent(NbLayoutComponent);

    overlayHostElement = document.createElement('div');
    overlayHostElement.style.width = '10px';
    overlayHostElement.style.height = '10px';
    overlayHostElement.style.backgroundColor = 'red';
    document.body.appendChild(overlayHostElement);

ConfirmDeleteComponent,
  ],
  imports: [
    BrowserModule,
    FormsModule,
    HttpClientModule,
    AppRoutingModule,
    TranslateModule.forRoot({
      loader: {
        provide: TranslateLoader,
        useFactory: (HttpLoaderFactory),
        deps: [HttpClient]
      }
    }),
    BrowserAnimationsModule,
    NbThemeModule.forRoot({ name: 'cosmic' }),
    NbLayoutModule,
    NbEvaIconsModule,
    NbSidebarModule.forRoot(), // NbSidebarModule.forRoot(), //if this is your app.module
    NbButtonModule,
    NbActionsModule,
    NbSearchModule,
    NbIconModule,
    NbMenuModule.forRoot(),
    NbTooltipModule,
    NbCardModule,
    NbInputModule,
    NbCheckboxModule,
    NbSelectModule,
    NbDialogModule.forRoot(),
    NgxMaskModule.forRoot(),
    NbToastrModule.forRoot(),

RoleListComponent,
    PermissionComponent,
    HomeComponent,
    LogoutComponent,
    UserProfileComponent,
    PictureStaticResourceComponent,
    AudioStaticResourceComponent,
    VideoStaticResourceComponent,
  ],
  imports: [
    FormsModule,
    HttpClientModule,
    BrowserModule,
    BrowserAnimationsModule,
    RouterModule.forRoot(routes, {useHash: true}),
    NbThemeModule.forRoot({name: 'corporate'}),
    NbLayoutModule,
    NbSidebarModule,
    NbMenuModule,
    ToasterModule,
    NbActionsModule,
    NbAlertModule,
    NbCardModule,
    NbUserModule,
    NbPopoverModule,
    NbSearchModule,
    NbContextMenuModule,
    NbCheckboxModule,
    FileUploadModule,
    NbProgressBarModule,
    PaginationModule.forRoot(),
    TooltipModule.forRoot(),

beforeEach(fakeAsync(() => {
    showTriggerStub = new Subject();
    hideTriggerStub = new Subject();
    triggerBuilderStub = {
      trigger() { return this },
      host() { return this },
      container() { return this },
      destroy() {},
      build() {
        return { show$: showTriggerStub, hide$: hideTriggerStub };
      },
    };

    TestBed.configureTestingModule({
      imports: [ RouterTestingModule.withRoutes([]), NbThemeModule.forRoot(), NbLayoutModule, NbSelectModule ],
      declarations: [ BasicSelectTestComponent ],
    });
    TestBed.overrideProvider(NbTriggerStrategyBuilderService, { useValue: triggerBuilderStub });

    fixture = TestBed.createComponent(BasicSelectTestComponent);
    fixture.detectChanges();
    flush();

    selectComponent = fixture.debugElement.query(By.directive(NbSelectComponent)).componentInstance;
  }));

NarikCoreModule.forRoot({
      configFilePath: "assets/app-config.json",
      defaultLang: "en",
      useDefaultLang: true,
      commandProcessor: DemoCommandProcessor
    }),
    NarikUiCoreModule,
    NarikAppCoreModule.forRoot({}),
    NarikJwtAuthenticationModule.forRoot({
      loginEndPoint: "api/account/Authenticate",
      logoutEndPoint: "api/account/Logout",
      refreshEndPoint: "api/account/Authenticate",
      tokenStorage: "localStorage",
      loginPageUrl: "/"
    }),
    NbThemeModule.forRoot(
      { name: "default" },
      undefined,
      undefined,
      NbLayoutDirection.LTR
    ),
    BrowserAnimationsModule,
    NarikClientStorageModule.forRoot(),
    NarikNgxAdmin,
    ShareModule
  ],
  providers: [
    {
      provide: MODULE_DATA_KEY,
      useValue: moduleKey
    },
    {

NarikCoreModule.forRoot({
      configFilePath: "assets/app-config.json",
      defaultLang: "en",
      useDefaultLang: true,
      commandProcessor: DemoCommandProcessor
    }),
    NarikUiCoreModule,
    NarikAppCoreModule.forRoot({}),
    NarikJwtAuthenticationModule.forRoot({
      loginEndPoint: "api/account/Authenticate",
      logoutEndPoint: "api/account/Logout",
      refreshEndPoint: "api/account/Authenticate",
      tokenStorage: "localStorage",
      loginPageUrl: "/"
    }),
    NbThemeModule.forRoot(
      { name: "default" },
      undefined,
      undefined,
      NbLayoutDirection.LTR
    ),
    BrowserAnimationsModule,
    NarikClientStorageModule.forRoot(),
    NarikNgxAdmin,
    ShareModule
  ],
  providers: [
    {
      provide: MODULE_DATA_KEY,
      useValue: moduleKey
    },
    {

function setupFixture(
    componentType: Type,
    columns: string[],
    data?: TreeNode[],
  ): ComponentFixture {

  TestBed.configureTestingModule({
    imports: [ NbThemeModule.forRoot(), NbTreeGridModule ],
    declarations: [ componentType ],
  });

  const fixture = TestBed.createComponent(componentType);
  fixture.componentInstance.columns = columns;
  if (data) {
    fixture.componentInstance.dataSource = data;
  }

  fixture.detectChanges();
  return fixture;
}

import { RouterModule } from '@angular/router';
import { NbEvaIconsModule } from '@nebular/eva-icons';
import { NbButtonModule, NbIconModule, NbLayoutModule, NbThemeModule } from '@nebular/theme';

import { AppRoutingModule } from './app-routing.module';
import { AppComponent } from './app.component';
import { NetworkSelectModule } from './components/network-select/network-select.module';
import { NetworkSelectService } from './components/network-select/network-select.service';
import { TaquitoService } from './taquito.service';

@NgModule({
  declarations: [AppComponent],
  imports: [
    BrowserModule,
    AppRoutingModule,
    NbThemeModule.forRoot(),
    BrowserAnimationsModule,
    NbLayoutModule,
    NbButtonModule,
    NbEvaIconsModule,
    NbIconModule,
    RouterModule,
    NetworkSelectModule,
  ],
  providers: [TaquitoService, NetworkSelectService],
  bootstrap: [AppComponent],
})
export class AppModule {}

beforeEach(() => {
    TestBed.configureTestingModule({
      imports: [
        RouterTestingModule.withRoutes([]),
        NoopAnimationsModule,
        NbThemeModule.forRoot(),
        NbSidebarModule.forRoot(),
        NbMenuModule.forRoot(),
      ],
      declarations: [ SidebarExpandTestComponent ],
    });
  });

LandingComponent,
    SlideAuthComponent,
    OdmDetailComponent
  ],
  imports: [
    BrowserModule,
    BrowserAnimationsModule,
    FormsModule,
    HttpModule,
    ROUTING,
    RouterModule,
    SharedModule,
    NbLayoutModule,
    NbSidebarModule,
    NbAlertModule,
    NbThemeModule.forRoot({ name: 'default' }),
  ],
  providers: [
    Provider,
    SignupService,
    LoginService,
    ListingService,
    BookingService,
    CheckinService,
    AuthGuardService,
    EthereumService,
    EmailService,
    OdmService,
    AuthService,
    XrpService,
    NbSidebarService
  ],