public async Task AuthorExistsAsync_Test() { using (var context = new LibraryContext(Utilities.TestDbContextOptions())) using (ILibraryRepository repository = new LibraryRepository(context)) { context.Authors.Add(new Author() { Id = new Guid("a1da1d8e-1988-4634-b538-a01709477b77"), FirstName = "Jens", LastName = "Lapidus", Genre = "Thriller", DateOfBirth = new DateTimeOffset(new DateTime(1974, 5, 24)), Books = new List <Book>() { new Book() { Id = new Guid("1325360c-8253-473a-a20f-55c269c20407"), Title = "Easy Money", Description = "Easy Money or Snabba cash is a novel from 2006 by Jens Lapidus. It has been a success in term of sales, and the paperback was the fourth best seller of Swedish novels in 2007." } } }); context.SaveChanges(); var exist = await repository.AuthorExistsAsync(Guid.Parse("a1da1d8e-1988-4634-b538-a01709477b77")); var nonExist = await repository.AuthorExistsAsync(Guid.Parse("f74d6899-9ed2-4137-9876-66b070553f8f")); Assert.True(exist); Assert.False(nonExist); } }