public async Task EnsuresArgumentsNotNull()
{
var gitHubClient = Substitute.For<IGitHubClient>();
var client = new ObservableEventsClient(gitHubClient);
await AssertEx.Throws<ArgumentNullException>(async () => await client.GetAllForRepository(null, "name"));
await AssertEx.Throws<ArgumentException>(async () => await client.GetAllForRepository("", "name"));
await AssertEx.Throws<ArgumentNullException>(async () => await client.GetAllForRepository("owner", null));
await AssertEx.Throws<ArgumentException>(async () => await client.GetAllForRepository("owner", ""));
}