public async Task GetAuthorIdByIdMethodShouldReturnNullIfPostIsDeleted() { var options = new DbContextOptionsBuilder <ForumDbContext>() .UseInMemoryDatabase(Guid.NewGuid().ToString()) .Options; var db = new ForumDbContext(options); var dateTimeProvider = new Mock <IDateTimeProvider>(); dateTimeProvider.Setup(dtp => dtp.Now()).Returns(new DateTime(2020, 3, 27)); var post = new Post { Id = 1, Title = "Test title 1", Description = "Test description 1", Type = PostType.Discussion, CategoryId = 1, AuthorId = "Test author id", IsDeleted = true, CreatedOn = dateTimeProvider.Object.Now(), DeletedOn = dateTimeProvider.Object.Now() }; await db.Posts.AddAsync(post); await db.SaveChangesAsync(); var postsService = new PostsService(db, null, null, dateTimeProvider.Object); var authorId = await postsService.GetAuthorIdByIdAsync(1); authorId.Should().BeNull(); }