Unit testing asynchronous code

Unit testing asynchronous code requires the same approach as writing good asynchronous C# code. If you need a refresher on how to work with async methods, you can review Chapter 5.

When writing a unit test for an async method, you will use the await keyword to wait for the method to complete. This requires that your unit test method is async and returns Task. Just like other C# code, creating async void methods is not permitted. Let’s look at a very simple test method:

[Fact]

private async Task GetBookAsync_Returns_A_Book()

{

    // Arrange

    BookService bookService = new();

    var bookId = 123;

    // Act

    var book = await bookService.GetBookAsync(bookId);

    // Assert

    Assert.NotNull(book);

    Assert.Equal(bookId, book.Id);

}

This probably...