public async Task EnsuresArgumentsNotNull()
            {
                var gitHubClient = Substitute.For<IGitHubClient>();
                var client = new ObservableEventsClient(gitHubClient);

                await AssertEx.Throws<ArgumentNullException>(async () => await client.GetUserPerformed(null));
                await AssertEx.Throws<ArgumentException>(async () => await client.GetUserPerformed(""));
            }
            public void RequestsCorrectUrl()
            {
                var gitHubClient = Substitute.For<IGitHubClient>();
                var client = new ObservableEventsClient(gitHubClient);

                client.GetUserPerformed("fake");

                gitHubClient.Connection.Received(1).GetAsync<List<Activity>>(new Uri("users/fake/events", UriKind.Relative), null, null);
            }