public async Task GetLatestActivityByIdMethodShouldReturnPostLatestActivity() { var guid = Guid.NewGuid().ToString(); var options = new DbContextOptionsBuilder <ForumDbContext>() .UseInMemoryDatabase(guid) .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 = guid, CreatedOn = dateTimeProvider.Object.Now(), }; await db.Posts.AddAsync(post); await db.SaveChangesAsync(); var postsService = new PostsService(db, null, null, dateTimeProvider.Object); var latestActivity = await postsService.GetLatestActivityByIdAsync(1); latestActivity.Should().Be("0m"); }