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

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

                client.GetForAnOrganization("fake", "org");

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