How to use the ngx-bootstrap.BsDropdownModule.forRoot function in ngx-bootstrap

import { NgModule, ModuleWithProviders } from '@angular/core';
import { NgxIntlTelInputComponent } from './ngx-intl-tel-input.component';
import { CommonModule } from '@angular/common';
import { BsDropdownModule, TooltipModule } from 'ngx-bootstrap';
import { FormsModule, ReactiveFormsModule } from '@angular/forms';
import { NgxIntlTelInputService } from './ngx-intl-tel-input.service';

@NgModule({
	declarations: [NgxIntlTelInputComponent],
	imports: [
		CommonModule,
		FormsModule,
		ReactiveFormsModule,
		BsDropdownModule.forRoot(),
		TooltipModule.forRoot()
	],
	exports: [NgxIntlTelInputComponent]
})
export class NgxIntlTelInputModule {
	static forRoot(): ModuleWithProviders {
		return {
			ngModule: NgxIntlTelInputModule,
			providers: [NgxIntlTelInputService]
		};
	}
}

beforeEach(async(() => {
    TestBed.configureTestingModule({
      imports: [
        CommonModule,
        SyndesisCommonModule.forRoot(),
        RouterTestingModule.withRoutes([]),
        ModalModule.forRoot(),
        BsDropdownModule.forRoot(),
        SyndesisStoreModule,
        ActionModule,
        ListModule,
        NotificationModule
      ],
      declarations: [IntegrationStatusComponent, IntegrationListComponent]
    }).compileComponents();
  }));

beforeEach(async(() => {
    TestBed.configureTestingModule({
      declarations: [ RgwDaemonListComponent ],
      imports: [
        DataTableModule,
        HttpClientTestingModule,
        BsDropdownModule.forRoot(),
        HttpClientModule
      ],
      providers: [ RgwDaemonService ]
    })
    .compileComponents();
  }));

const containers = [
  PermissionComponent,
  ...fromContainers.containers
]

@NgModule({
  imports: [
    CommonModule,
    FormsModule,
    ReactiveFormsModule,
    TranslateModule,
    NgxDatatableModule,
    CommonPipesModule,
    TooltipModule.forRoot(),
    BsDropdownModule.forRoot(),
    SweetAlert2Module,
    AngularMultiSelectModule,
    PermissionRoutingModule
  ],
  declarations: containers,
  providers: [
    PermissionService,
    PermissionApiClient,
    AccessPermissionSandbox
  ]
})
export class PermissionModule { }

const containers = [
  RoleComponent,
  ...fromContainers.containers
]

@NgModule({
  imports: [
    CommonModule,
    FormsModule,
    ReactiveFormsModule,
    TranslateModule,
    NgxDatatableModule,
    CommonPipesModule,
    TooltipModule.forRoot(),
    BsDropdownModule.forRoot(),
    SweetAlert2Module,
    AngularMultiSelectModule,
    RoleRoutingModule
  ],
  declarations: containers,
  providers: [
    RoleService,
    RoleApiClient,
    AccessRoleSandbox,
    AccessPermissionSandbox
  ]
})
export class RoleModule { }

beforeEach(async(() => {
    TestBed.configureTestingModule({
      declarations: [
        RgwUserListComponent,
        RgwUserDetailsComponent
      ],
      imports: [
        HttpClientModule,
        BsDropdownModule.forRoot(),
        TabsModule.forRoot(),
        SharedModule
      ]
    })
    .compileComponents();
  }));

beforeEach( async(() => {
    activeRoute = new MockActivatedRoute();
    TestBed.configureTestingModule({
      imports: [
        RouterTestingModule.withRoutes([]),
        ClipboardModule,
        BsDropdownModule.forRoot(),
        ReactiveFormsModule,
        TooltipModule.forRoot(),
        FormsModule,
        NgxPaginationModule,
      ],
      declarations:   [
        AboutComponent,
        AboutDetailsComponent,
        LoaderComponent,
        DATAFLOW_PAGE,
        DATAFLOW_LIST,
        PagerComponent,
        TippyDirective
      ],
      providers: [
        { provide: AboutService, useValue: aboutService },

FooterComponent,
    HeaderComponent,
    SidebarComponent,
    NotfoundComponent,
    LoginComponent,
    RegisterComponent
  ],
  imports: [
    BrowserModule,
    FormsModule,
    ReactiveFormsModule,
    HttpClientModule,
    AppRoutingModule,
    NgxDatatableModule,
    CollapseModule.forRoot(),
    BsDropdownModule.forRoot(),
    ModalModule.forRoot(),
    PaginationModule.forRoot(),
    BsDatepickerModule.forRoot(),
    ToastNoAnimationModule,
    ToastrModule.forRoot({
      toastComponent: ToastNoAnimation,
      maxOpened: 1,
      autoDismiss: true
    }),
    TranslateModule.forRoot({
      loader: {
        provide: TranslateLoader,
        useFactory: createTranslateLoader,
        deps: [HttpClient]
      }
    })

beforeEach(async(() => {
    TestBed.configureTestingModule({
      imports: [
        FormsModule,
        BsDropdownModule.forRoot(),
        PaginationModule.forRoot()
      ],
      declarations: [
        NgxMagicTableComponent,
        NgxMagicTableContentPlaceholderComponent,
        NgxMagicTableSortedColumnDirective,
        NgxMagicTableBindDataDirective
      ],
      providers: [
        { provide: NgxMagicTableObjectUtilsService, useClass: MockNgxMagicTableObjectUtilsService }
      ]
    })
    .compileComponents()
    .then(() => {
      fixture = TestBed.createComponent(NgxMagicTableComponent);
      component = fixture.componentInstance;

import { StreamsUtilsComponent } from './streams-utils/streams-utils.component';
import { StreamsImportComponent } from './streams-utils/streams-import/streams-import.component';
import { StreamsExportComponent } from './streams-utils/streams-export/streams-export.component';
import { StreamsUtilsService } from './streams-utils/streams-utils.service';

@NgModule({
  imports: [
    StreamsRoutingModule,
    SharedModule,
    NgxPaginationModule,
    ReactiveFormsModule,
    AlertModule.forRoot(),
    ModalModule.forRoot(),
    PopoverModule.forRoot(),
    TooltipModule.forRoot(),
    BsDropdownModule.forRoot(),
    AppsModule,
    FloModule,
    AuthModule,
    ProgressbarModule,
  ],
  declarations: [
    StreamsComponent,
    StreamCreateComponent,
    StreamComponent,
    StreamDeployComponent,
    StreamCreateDialogComponent,
    StreamPropertiesDialogComponent,
    StreamNodeComponent,
    StreamGraphDefinitionComponent,
    InstanceDotComponent,
    MessageRateComponent,