Having the exact same issue. In my TestBed config I added this to the providers. { provide : TranslateLoader, useFactory: (http: Http) => new TranslateStaticLoader (http, '/assets/i18n' , '.json' ), deps: [Http] } and then in my test it( 'should create the app' , inject([TranslateService], (translate) => { let fixture = TestBed.createComponent(AppComponent); let app = fixture.debugElement.componentInstance; expect(app).toBeTruthy(); })); However, my karma test server returns a 404 for en.json. Proxies in karma conf seem to do shag all. So frustrating as I know the solution is probably very simple.