public void incrementLikeCount_Success() { Mock <IFileOperation> mockFile = new Mock <IFileOperation>(); mockFile.Setup(x => x.ReadTheBookFromFileChangeTheLikeCount(It.IsAny <Domain.Book>(), It.IsAny <Domain.User>())).Returns(new BookResult { isSuccess = true, message = "success" }); BookOperation bookOperation = new BookOperation(mockFile.Object); Book book = new Book(); User user = new User(); BookResult result = bookOperation.incrementLikeCount(book, user); Assert.True(result.isSuccess); }