public async Task GetByThread_ReturnsAllPosts_WhenProvidedValidId() { // Arrange var posts = new List <ForumPost> { new ForumPost { Content = "test", Id = 11, ThreadId = 2 }, new ForumPost { Content = "test", Id = 22, ThreadId = 2 } }; _postsRepositoryMock.Setup(x => x.GetByThread(It.IsAny <int>())).ReturnsAsync(posts); // Act IReadOnlyCollection <PostDetailsModel> result = await _postsService.GetByThread(2); // Assert Assert.That(result.Count, Is.EqualTo(2)); Assert.IsTrue(result.Any(x => x.Id == 11)); Assert.IsTrue(result.Any(x => x.Id == 22)); }