@Test
    public void testDigraphAmbiguousSingleLengthAncestor() {
        In in = new In("src\\tests\\data\\digraph-ambiguous-ancestor.txt");
        SAP sap_amb = new SAP(new Digraph(in));
        assertEquals(1, sap_amb.length(0, 10));
        assertEquals(1, sap_amb.length(10, 0));
        assertEquals(10, sap_amb.ancestor(0, 10));
        assertEquals(10, sap_amb.ancestor(10, 0));
        assertEquals(5, sap_amb.length(0, 6));
        assertEquals(5, sap_amb.length(6, 0));
        int ancestor = sap_amb.ancestor(0, 6);
        assertTrue( ancestor == 2 || ancestor == 7);
        ancestor = sap_amb.ancestor(6, 0);
        assertTrue( ancestor == 2 || ancestor == 7);
    }