title: NullInjectorError: No provider for custom component - Adding to providers doesn't work
body: <p>I am having errors thrown when I am attempting tests...</p>
  
  <p>I have read many similar related issues, but adding my custom LoginComponent to app.module.ts providers doesn't help? It is already in the imports section.</p>
  
  <p><strong>app.module.ts</strong></p>
  
  <pre><code>@NgModule({
    declarations: [
      AppComponent,
      LoginComponent,
    ],
    imports: [
      BrowserModule,
      FormsModule,
      HttpClientModule
    ],
    providers: [
      {
        provide: HTTP_INTERCEPTORS,
        useClass: AppHttpInterceptor,
        multi: true
      }
    ],
    bootstrap: [AppComponent]
  })
  export class AppModule { }
  </code></pre>
  
  <p><strong>login.component.spec.ts</strong> (summarised)</p>
  
  <pre><code>import {async, ComponentFixture, inject, TestBed} from '@angular/core/testing';
  
  import {LoginComponent} from './login.component';
  import {FormsModule, NgForm} from '@angular/forms';
  import {HttpClientModule} from "@angular/common/http";
  import {AuthService} from "../../services/auth/auth.service";
  
  describe('LoginComponent', () =&gt; {
     beforeEach(async(() =&gt; {
      TestBed.configureTestingModule({
        declarations: [LoginComponent],
        imports: [FormsModule, HttpClientModule, FormsModule]
      }).compileComponents();
  
      fixture = TestBed.createComponent(LoginComponent);
      component = fixture.componentInstance;
    }));
  
      it('Attempt login with various invalid forms', 
        inject([LoginComponent, AuthService],
        (loginComp: LoginComponent, authServ: AuthService) =&gt; {
  
      // Testing stuff here
  
      }));
  
  }
  </code></pre>