@Test
 public void matches_zero_occurrences() {
   final Ndfa ndfa = ndfaFactory.create();
   assertTrue(ndfa.isAccepting());
   assertTrue(ndfa.isAlive());
   ndfa.onChar('p');
   assertTrue(!ndfa.isAccepting());
   assertTrue(!ndfa.isAlive());
 }
 @Test
 public void matches_single_character() {
   final Ndfa ndfa = ndfaFactory.create();
   assertTrue(!ndfa.isAccepting());
   assertTrue(ndfa.isAlive());
   ndfa.onChar('c');
   assertTrue(ndfa.isAccepting());
   assertTrue(ndfa.isAlive());
   ndfa.onChar('d');
   assertTrue(!ndfa.isAccepting());
   assertTrue(!ndfa.isAlive());
 }