public void ExchangeTest()
{
var heap = new FibonacciHeap <int>((a, b) => a < b);
var node1 = new FibonacciNode <int>(12);
var node2 = new FibonacciNode <int>(11);
heap.Exchange(ref node1, ref node2);
Assert.AreEqual(node1.Key, 11);
}