@Test
public void testSignalVertex() {

  final SignalVertex sg1 = insertNewSignalVertex(irdag, oneToOneEdge);
  mustPass();
  final SignalVertex sg2 = insertNewSignalVertex(irdag, shuffleEdge);
  mustPass();
  irdag.delete(sg1);
  mustPass();
  irdag.delete(sg2);
  mustPass();
}