public async Task EnsuresNonNullArguments()
            {
                var client = new ObservableRepositoryBranchesClient(Substitute.For<IGitHubClient>());
                var update = new BranchUpdate();

                Assert.Throws<ArgumentNullException>(() => client.Edit(null, "repo", "branch", update));
                Assert.Throws<ArgumentNullException>(() => client.Edit("owner", null, "branch", update));
                Assert.Throws<ArgumentNullException>(() => client.Edit("owner", "repo", null, update));
                Assert.Throws<ArgumentNullException>(() => client.Edit("owner", "repo", "branch", null));

                Assert.Throws<ArgumentNullException>(() => client.Edit(1, null, update));
                Assert.Throws<ArgumentNullException>(() => client.Edit(1, "branch", null));

                Assert.Throws<ArgumentException>(() => client.Edit("", "repo", "branch", update));
                Assert.Throws<ArgumentException>(() => client.Edit("owner", "", "branch", update));
                Assert.Throws<ArgumentException>(() => client.Edit("owner", "repo", "", update));

                Assert.Throws<ArgumentException>(() => client.Edit(1, "", update));
            }
            public void RequestsTheCorrectUrlWithRepositoryId()
            {
                var github = Substitute.For<IGitHubClient>();
                var client = new ObservableRepositoryBranchesClient(github);
                var update = new BranchUpdate();

                client.Edit(1, "branch", update);

                github.Repository.Branch.Received(1).Edit(1, "branch", update);
            }