[Fact] public void GetPostById_ShouldContactBlogPostGrain()
        {
            var postGrain = new Mock <IBlogPostGrain>();

            var post = new BlogPost {
                BlogPostId = Guid.NewGuid()
            };

            _clusterClient.Setup(c => c.GetGrain <IBlogPostGrain>(post.BlogPostId, null))
            .Returns(() => postGrain.Object);

            postGrain.Setup(g => g.Find()).Returns(() => Task.FromResult(post));

            _blogPostService.GetPostById(post.BlogPostId)
            .Should().Be(post, "because that's what we requested");

            _clusterClient.Verify(c => c.GetGrain <IBlogPostGrain>(post.BlogPostId, null), Times.Once(),
                                  "because we need to fetch the grain");

            postGrain.Verify(g => g.Find(), Times.Once(),
                             "because we need to fetch the post");

            _clusterClient.VerifyNoOtherCalls();
            postGrain.VerifyNoOtherCalls();
        }