public void SeeASheetPartDetails_successful() { var mockUnitOfWork = new Mock <ILibraryUnitOfWork>(); mockUnitOfWork.Setup(u => u.SheetPartRepository.GetById(It.IsAny <int>())) .Returns(new SheetPartTO { Id = 1, Path = $@"\Files\BestOf\Saxophone" }); var sut = new MusicianUC(mockUnitOfWork.Object, null); var result = sut.SeeASheetPartDetails(1); Assert.IsNotNull(result); mockUnitOfWork.Verify(u => u.SheetPartRepository.GetById(1), Times.Once); }