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

                await Assert.ThrowsAsync<ArgumentNullException>(() => client.GetSha1(null, "name", "reference").ToTask());
                await Assert.ThrowsAsync<ArgumentNullException>(() => client.GetSha1("owner", null, "reference").ToTask());
                await Assert.ThrowsAsync<ArgumentNullException>(() => client.GetSha1("owner", "name", null).ToTask());
            }
            public void EnsuresNonEmptyArguments()
            {
                var client = new ObservableRepositoryCommitsClient(Substitute.For<IGitHubClient>());

                Assert.ThrowsAsync<ArgumentException>(() => client.GetSha1("", "name", "reference").ToTask());
                Assert.ThrowsAsync<ArgumentException>(() => client.GetSha1("owner", "", "reference").ToTask());
                Assert.ThrowsAsync<ArgumentException>(() => client.GetSha1("owner", "name", "").ToTask());
            }
            public void GetsCorrectUrl()
            {
                var gitHubClient = Substitute.For<IGitHubClient>();
                var client = new ObservableRepositoryCommitsClient(gitHubClient);

                client.GetSha1("owner", "name", "reference");

                gitHubClient
                    .Received()
                    .Repository
                    .Commit
                    .GetSha1("owner", "name", "reference");
            }
            public void EnsuresNonNullArguments()
            {
                var connection = Substitute.For<IGitHubClient>();
                var client = new ObservableRepositoryCommitsClient(connection);

                Assert.Throws<ArgumentNullException>(() => client.GetSha1(null, "name", "ref"));
                Assert.Throws<ArgumentNullException>(() => client.GetSha1("owner", null, "ref"));
                Assert.Throws<ArgumentNullException>(() => client.GetSha1("owner", "name", null));

                Assert.Throws<ArgumentNullException>(() => client.GetSha1(1, null));

                Assert.Throws<ArgumentException>(() => client.GetSha1("", "name", "ref"));
                Assert.Throws<ArgumentException>(() => client.GetSha1("owner", "", "ref"));
                Assert.Throws<ArgumentException>(() => client.GetSha1("owner", "name", ""));

                Assert.Throws<ArgumentException>(() => client.GetSha1(1, ""));
            }
            public void RequestsCorrectUrlWithRepositoryId()
            {
                var gitHubClient = Substitute.For<IGitHubClient>();
                var client = new ObservableRepositoryCommitsClient(gitHubClient);

                client.GetSha1(1, "ref");

                gitHubClient.Received().Repository.Commit.GetSha1(1, "ref");
            }