public async Task EnsuresNonNullArguments()
            {
                var client = new ObservableRepositoryBranchesClient(Substitute.For<IGitHubClient>());
                var newContexts = new List<string>() { "test" };

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

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

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

                Assert.Throws<ArgumentException>(() => client.AddRequiredStatusChecksContexts(1, "", newContexts));
            }
            public void RequestsTheCorrectUrlWithRepositoryId()
            {
                var gitHubClient = Substitute.For<IGitHubClient>();
                var client = new ObservableRepositoryBranchesClient(gitHubClient);
                var newContexts = new List<string>() { "test" };

                client.AddRequiredStatusChecksContexts(1, "branch", newContexts);

                gitHubClient.Repository.Branch.Received()
                    .AddRequiredStatusChecksContexts(1, "branch", newContexts);
            }