Variable[] vars = new Variable [4];
    for (int i = 0; i < vars.length; i++) {
      vars[i] = new Variable(3);
    }
    HashVarSet c1 = new HashVarSet (vars);
    HashVarSet c2 = new HashVarSet (vars);
    assertTrue(c1.equals (c2));
    assertTrue(c2.equals (c1));
    assertEquals (c1.hashCode(), c2.hashCode ());
  }