public void Authenticate() { var repositoryMock = new Mock <IBusinessRepository>(); var accountManagerMock = new Mock <IAccountManager <Business> >(); accountManagerMock.Setup(x => x.Authenticate(business.Email, password, repositoryMock.Object)).Returns(new Business()); IBusinessService businessService = new BusinessService(repositoryMock.Object, null, accountManagerMock.Object, null); Business result = businessService.Authenticate(business.Email, password); Assert.NotNull(result); }