CreateReply() public method

Creates a comment on a pull request review as a reply to another comment.
http://developer.github.com/v3/pulls/comments/#create-a-comment
public CreateReply ( long repositoryId, int number, PullRequestReviewCommentReplyCreate comment ) : IObservable
repositoryId long The Id of the repository
number int The pull request number
comment PullRequestReviewCommentReplyCreate The comment
return IObservable
            public async Task EnsuresNonNullArguments()
            {
                var gitHubClient = Substitute.For<IGitHubClient>();
                var client = new ObservablePullRequestReviewCommentsClient(gitHubClient);

                string body = "Comment content";
                int inReplyTo = 7;

                var comment = new PullRequestReviewCommentReplyCreate(body, inReplyTo);

                Assert.Throws<ArgumentNullException>(() => client.CreateReply(null, "name", 1, comment));
                Assert.Throws<ArgumentNullException>(() => client.CreateReply("owner", null, 1, comment));
                Assert.Throws<ArgumentNullException>(() => client.CreateReply("owner", "name", 1, null));

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

                Assert.Throws<ArgumentException>(() => client.CreateReply("", "name", 1, comment));
                Assert.Throws<ArgumentException>(() => client.CreateReply("owner", "", 1, comment));
            }
            public void PostsToCorrectUrlWithRepositoryId()
            {
                var gitHubClient = Substitute.For<IGitHubClient>();
                var client = new ObservablePullRequestReviewCommentsClient(gitHubClient);

                var comment = new PullRequestReviewCommentReplyCreate("Comment content", 9);

                client.CreateReply(1, 13, comment);

                gitHubClient.PullRequest.ReviewComment.Received().CreateReply(1, 13, comment);
            }