public void CreateBook_ValidBookSuppliedAsParameter_CreatesAndReturnsNewBook (string title, int authorId, decimal price) { var validInput = new Book { Title = title, AuthorId = authorId, Price = price }; var highestCurrentBookId = AllBooks.Max(book => book.Id); var expectedResult = new Book { Title = title, AuthorId = authorId, Price = price, Id = highestCurrentBookId + 1 }; var result = BookRepository.CreateBook(validInput); result.Should().BeEquivalentTo(expectedResult); }