public async Task EnsuresArgumentsNotNull()
            {
                var gitHubClient = Substitute.For<IGitHubClient>();
                var client = new ObservableTreesClient(gitHubClient);

                AssertEx.Throws<ArgumentNullException>(async () => await client.Create(null, "name", new NewTree()));
                AssertEx.Throws<ArgumentException>(async () => await client.Create("", "name", new NewTree()));
                AssertEx.Throws<ArgumentNullException>(async () => await client.Create("owner", null, new NewTree()));
                AssertEx.Throws<ArgumentException>(async () => await client.Create("owner", "", new NewTree()));
                AssertEx.Throws<ArgumentNullException>(async () => await client.Create("owner", "name", null));
            }
            public void CreatesFromClientIssueIssue()
            {
                var newTree = new NewTree();
                var gitHubClient = Substitute.For<IGitHubClient>();
                var client = new ObservableTreesClient(gitHubClient);

                client.Create("fake", "repo", newTree);

                gitHubClient.Git.Tree.Received().Create("fake", "repo", newTree);
            }
            public async Task EnsuresNonNullArguments()
            {
                var client = new ObservableTreesClient(Substitute.For<IGitHubClient>());

                Assert.Throws<ArgumentNullException>(() => client.Create(null, "name", new NewTree()));
                Assert.Throws<ArgumentNullException>(() => client.Create("owner", null, new NewTree()));
                Assert.Throws<ArgumentNullException>(() => client.Create("owner", "name", null));

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

                Assert.Throws<ArgumentException>(() => client.Create("", "name", new NewTree()));
                Assert.Throws<ArgumentException>(() => client.Create("owner", "", new NewTree()));
            }
            public void RequestsCorrectUrlWithRepositoryId()
            {
                var newTree = new NewTree();
                var gitHubClient = Substitute.For<IGitHubClient>();
                var client = new ObservableTreesClient(gitHubClient);

                client.Create(1, newTree);

                gitHubClient.Git.Tree.Received().Create(1, newTree);
            }