class Rectangle{
  private Integer width = 0;
  private Integer height = 0; 

  Rectangle(Integer _width, Integer _height){
    width = _width;
    height = _height; 
  }

  public Integer area(){
    return width * height; 
  }
}

class Square extends Rectangle{
  Square(Integer side){
    super(side, side); 
  }
}

/* ...assume the following is written to in a proper test class */
@Test
public Boolean describe_area() {
  Square sq = new Square(5,5); 
  sq.width = 6; 

  Assert.assertTrue(sq.area() == 30);
}