public void testGetCommonAncestor(){
IndexedWord common = graph.getCommonAncestor(graph.getNodeByIndex(43), graph.getNodeByIndex(44));
assertEquals(45, common.index());
common = graph.getCommonAncestor(graph.getNodeByIndex(41), graph.getNodeByIndex(39));
assertEquals(41, common.index());
common = graph.getCommonAncestor(graph.getNodeByIndex(39), graph.getNodeByIndex(41));
assertEquals(41, common.index());
common = graph.getCommonAncestor(graph.getNodeByIndex(40), graph.getNodeByIndex(42));