public void MultipleElementSequenceDoesNotIterate()
{
IEnumerableWithCount<int> source = new ThrowingEnumerable(2);
Assert.Throws<InvalidOperationException>(() => source.SingleOrDefault());
}
public void EmptySequenceDoesNotIterate()
{
IEnumerableWithCount<int> source = new ThrowingEnumerable(0);
Assert.AreEqual(0, source.SingleOrDefault());
}