public void RequestsCorrectUrl()
            {
                var gitHubClient = Substitute.For<IGitHubClient>();
                var client = new ObservableIssueCommentsClient(gitHubClient);

                client.GetForIssue("fake", "repo", 3);

                gitHubClient.Connection.Received(1).Get<List<IssueComment>>(
                    new Uri("repos/fake/repo/issues/3/comments", UriKind.Relative), null, null);
            }
            public async Task EnsuresArgumentsNotNull()
            {
                var gitHubClient = Substitute.For<IGitHubClient>();
                var client = new ObservableIssueCommentsClient(gitHubClient);

                await AssertEx.Throws<ArgumentNullException>(async () => await client.GetForIssue(null, "name", 1));
                await AssertEx.Throws<ArgumentException>(async () => await client.GetForIssue("", "name", 1));
                await AssertEx.Throws<ArgumentNullException>(async () => await client.GetForIssue("owner", null, 1));
                await AssertEx.Throws<ArgumentException>(async () => await client.GetForIssue("owner", "", 1));
            }