public void GetAll_ShouldReturnAllPosts()
        {
            var posts = new List <BlogPost> {
                new BlogPost {
                    BlogPostId = Guid.NewGuid()
                },
                new BlogPost {
                    BlogPostId = Guid.NewGuid()
                },
                new BlogPost {
                    BlogPostId = Guid.NewGuid()
                },
                new BlogPost {
                    BlogPostId = Guid.NewGuid()
                }
            };

            _inMemoryContext.Posts.AddRange(posts);
            _inMemoryContext.SaveChanges();

            var expected = posts.Select(p => (IBlogPost)p).ToList();

            _blogPostRepository.GetAll().Result.Should().BeEquivalentTo(expected,
                                                                        "because we expect to get all the posts stored in the database");
        }