public void ClearList()
{
var proxy = new ListProxy(Enumerable.Range(0, 100).ToList());
var enumerator = proxy.GetEnumerator();
enumerator.MoveNext();
enumerator.MoveNext();
proxy.Clear();
Assert.AreEqual(100, proxy.Count);
Assert.That(() => enumerator.MoveNext(), Throws.InvalidOperationException);
}