public void Decrease_MiddleElement_ExtractsAllElementsCorrectly()
{
var heap = new PairingHeap <int>();
heap.Insert(2);
var pointer = heap.Insert(1);
heap.Insert(0);
heap.Decrease(pointer, -1);
var elements = ExtractAll(heap).ToArray();
Assert.That(elements, Is.EqualTo(new[] { -1, 0, 2 }));
}