public void CanClear()
{
var q = new CappedQueue <int>(3);
q.Enqueue(1);
q.Enqueue(2);
q.Enqueue(3);
q.Enqueue(4);
q.Clear();
q.Clear(); // idempotent
Assert.Equal(0, q.Count);
Assert.Equal(3, q.Capacity);
}
