public NodeModel commonAncestor() {
		return commonAncestor;
    }
@Test
	public void oneLevelAncestor(){
		final NodeModel parent = root();
		final NodeModel node1 = new NodeModel("node1", map);
		parent.insert(node1);
		final NodeModel node2 = new NodeModel("node2", map);
		parent.insert(node2);
		NodeModel commonAncestor = new NodeRelativePath(node1, node2).commonAncestor();
		assertThat(commonAncestor, equalTo(parent));
	}