private void CheckDeque(IDeque <Type> c)
{
builder.ExpectThat(c.Peek(), Is.Null);
builder.ExpectException <InvalidOperationException> (() => c.Dequeue());
if (c.ToArray() != null)
{
builder.ExpectThat(c.ToArray().Length, Is.EqualTo(0));
}
builder.ExpectThat(c.GetEnumerator().MoveNext(), Is.False);
builder.ExpectThat(c.GetDescendingEnumerator().MoveNext(), Is.False);
}