public async Task Update_Book_Authors()
{
var book = await BookHelpers.CreateValidBookWithAllProperties();
var repository = new BookRepository(_fixture.Context);
(await repository.ExistsAsync(book.Id)).Should().BeTrue();
var sut = await repository.LoadAsync(book.Id);
var bookId = sut.Id;
sut.Should().NotBeNull();
sut.Authors.Count.Should().Be(2);
var author1 = await AuthorHelpers.CreateValidAuthor();
var author2 = await AuthorHelpers.CreateValidAuthor();
var authors = new List <Author> {
author1, author2
};
await BookHelpers.UpdateAuthors(sut.Id, authors);
sut = await repository.LoadAsync(book.Id);
await _fixture.Context.Entry(sut).ReloadAsync();
sut.Authors.Count.Should().Be(4);
sut.Id.Should().Be(bookId);
}