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

                client.Get(1, "label");

                gitHubClient.Issue.Labels.Received().Get(1, "label");
            }
            public async Task EnsuresNonNullArguments()
            {
                var client = new ObservableIssuesLabelsClient(Substitute.For <IGitHubClient>());

                Assert.Throws <ArgumentNullException>(() => client.Get(null, "name", "label"));
                Assert.Throws <ArgumentNullException>(() => client.Get("owner", null, "label"));
                Assert.Throws <ArgumentNullException>(() => client.Get("owner", "name", null));

                Assert.Throws <ArgumentNullException>(() => client.Get(1, null));

                Assert.Throws <ArgumentException>(() => client.Get("", "name", "label"));
                Assert.Throws <ArgumentException>(() => client.Get("owner", "", "label"));
                Assert.Throws <ArgumentException>(() => client.Get("owner", "name", ""));

                Assert.Throws <ArgumentException>(() => client.Get(1, ""));
            }