@Test
public void testSelfCycle() {

	Node node1 = new Node(1, 1);
	Map<Node, Collection<Node>> nodeMap = GraphUtil.getNodeMap(
		Collections.singleton(node1),
		Collections.singletonMap(
			node1, Collections.singletonList(new Edge(node1, node1))));
	Assert.assertEquals(
		Collections.singleton(node1), nodeMap.remove(new Node(0, 0)));
	Assert.assertTrue(nodeMap.toString(), nodeMap.isEmpty());
}