public void Edit_GivenBookIdAndNewTitle_ChangesBookId() { // Arrange var bookLibrary = new BookLibrary(); var expectedBookTitle = "War and Peace"; bookLibrary.Add("A Tale of Two Cities"); bookLibrary.Add("Fellowship of the Ring"); bookLibrary.Add("Pride and Prejudice and Zombies"); // Act bookLibrary.Edit(1, expectedBookTitle); // Assert var actual = bookLibrary.Get(1); actual.Title.Should().Be(expectedBookTitle); }