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

                AssertEx.Throws<ArgumentNullException>(async () => await
                    client.Create(null, "name", new NewMilestone("title")));
                AssertEx.Throws<ArgumentException>(async () => await
                    client.Create("", "name", new NewMilestone("x")));
                AssertEx.Throws<ArgumentNullException>(async () => await
                    client.Create("owner", null, new NewMilestone("x")));
                AssertEx.Throws<ArgumentException>(async () => await
                    client.Create("owner", "", new NewMilestone("x")));
                AssertEx.Throws<ArgumentNullException>(async () => await
                    client.Create("owner", "name", null));
            }
            public void CreatesFromClientIssueMilestone()
            {
                var newMilestone = new NewMilestone("some title");
                var gitHubClient = Substitute.For<IGitHubClient>();
                var client = new ObservableMilestonesClient(gitHubClient);

                client.Create("fake", "repo", newMilestone);

                gitHubClient.Issue.Milestone.Received().Create("fake", "repo", newMilestone);
            }