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

                client.Get("fake", "repo", "123456ABCD");

                gitHubClient.Git.Tree.Received().Get("fake", "repo", "123456ABCD");
            }
            public void RequestsCorrectUrlWithRepositoryId()
            {
                var gitHubClient = Substitute.For<IGitHubClient>();
                var client = new ObservableTreesClient(gitHubClient);

                client.Get(1, "123456ABCD");

                gitHubClient.Git.Tree.Received().Get(1, "123456ABCD");
            }
            public async Task EnsuresNonNullArguments()
            {
                var client = new ObservableTreesClient(Substitute.For<IGitHubClient>());

                Assert.Throws<ArgumentNullException>(() => client.Get(null, "name", "123456ABCD"));
                Assert.Throws<ArgumentNullException>(() => client.Get("owner", null, "123456ABCD"));
                Assert.Throws<ArgumentNullException>(() => client.Get("owner", "name", null));

                Assert.Throws<ArgumentNullException>(() => client.Get(1, null));
                
                Assert.Throws<ArgumentException>(() => client.Get("", "name", "123456ABCD"));
                Assert.Throws<ArgumentException>(() => client.Get("owner", "", "123456ABCD"));
                Assert.Throws<ArgumentException>(() => client.Get("owner", "name", ""));

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