public void PostsToTheCorrectUrl()
        {
            var connection = Substitute.For<IApiConnection>();
            var client = new GistsClient(connection);

            var updateGist = new GistUpdate();
            updateGist.Description = "my newly updated gist";
            var gistFileUpdate = new GistFileUpdate 
            { 
                NewFileName = "myNewGistTestFile.cs",
                Content = "new GistsClient(connection).Edit();"
            };

            updateGist.Files.Add("myGistTestFile.cs", gistFileUpdate);

            client.Edit("1", updateGist);

            connection.Received().Patch<Gist>(Arg.Is<Uri>(u => u.ToString() == "gists/1"), Arg.Any<object>());
        }