title: Angular2 FormBuilder unit testing
body: <p>I have two question in regards to mocking Formbuilder in Angular2.</p>
  
  <p>1) How do I mock formBuilder in a spec? Are there any given mocks that we can use? I would like to for instance, update the values of a form in my spec, and then test to see if the form is still valid - or test the functionality of methods in my component that update a formbuilder group, or determine if a formbuilder group is valid.</p>
  
  <p>2) How do I deal with the following error given that fb is a DI injection of Formbuilder in a spec?</p>
  
  <p><code>null is not an object (evaluating 'this.fb.group')</code></p>
  
  <p>when the component is as follows:</p>
  
  <pre><code>export class LoginComponent implements OnInit {
    constructor( private fb: FormBuilder ) {}
  
    ngOnInit() {
      this.loginForm = this.fb.group({
        'email': this.user.email,
        'password': this.user.password
      });
    }
  }
  </code></pre>