public async Task EnsuresNonNullArguments()
        {
            var client = new GistCommentsClient(Substitute.For<IApiConnection>());

            await AssertEx.Throws<ArgumentNullException>(async () => await client.Create("24", null));
            await AssertEx.Throws<ArgumentException>(async () => await client.Create("24", ""));
        }
        public async Task PostsToCorrectUrl()
        {
            var comment = "This is a comment.";
            var connection = Substitute.For<IApiConnection>();
            var client = new GistCommentsClient(connection);

            await client.Create("24", comment);

            connection.Received().Post<GistComment>(Arg.Is<Uri>(u => u.ToString() == "gists/24/comments"), Arg.Is<BodyWrapper>(x => x.Body == comment));
        }