// too far for this method
common = graph.getCommonAncestor(graph.getNodeByIndex(10), graph.getNodeByIndex(42));
assertEquals(null, common);
common = graph.getCommonAncestor(graph.getNodeByIndex(10), graph.getNodeByIndex(10));
assertEquals(10, common.index());
common = graph.getCommonAncestor(graph.getNodeByIndex(40), graph.getNodeByIndex(40));
assertEquals(40, common.index());
// a couple tests at the top of the graph