angular2 testing: Can’t bind to ‘ngModel’ since it isn’t a known property of ‘input’

You need to import the FormsModule into the TestBed configfuration.

import { FormsModule } from '@angular/forms';

TestBed.configureTestingModule({
  imports: [ FormsModule ],
  declarations: [
    AppComponent
  ],
  providers:[AppService]
});

What you are doing with the TestBed is configuring a NgModule from scratch for the test environment. This allows you to only add what is needed for the test without having unnecessary outside variables that may affect the test.