Karma unit testing error: Unexpected value imported by the module. Please add a @NgModule annotation

You are injecting MatDialogRef in component:

constructor(private dialogRef: MatDialogRef<Mytest1Component>) { }

So the testBed expects the same to be injected as provider to the TestBed. Or you can also provide a MockDialogueService to it.

beforeEach(async(() => {
    TestBed.configureTestingModule({
        declarations: [ Mytest1Component ],
        providers: [ MatDialogRef ],
    })
    .compileComponents();
}));