class TestIntList {

  /** Sample IntList values */
  static final oneElt  = new Cons(1, Empty.ONLY);
  static final twoElts = new Cons(5, oneElt);
  static final threeElts = new Cons(-10, twoElts);

  /** Test the sum() method, assuming that ans is 
   *  the correct answer for this.sum() */
  void testSum(int ans) {

    int result = sum();	
    System.out.println("computed sum of " + this + " = " + sum());
    if (result != ans)  
      System.out.println("FAILURE: correct answer is " + ans);
  }

  /** Test driver method */
  public void test() {
    Empty.ONLY.testSum(0);
    Cons.oneElt.testSum(1);
    Cons.twoElts.testSum(6);
    Cons.threeElts.testSum(-4);
  }
}