@Test
 public void removesAnElementFromTheMiddle() {
   fillVector();
   Circle s = new Circle(2.0);
   vector.remove(s);
   assertFalse(vector.contains(s));
 }
 @Test
 public void removesAnElementFromTheFront() {
   Circle s = new Circle(2.0);
   vector.add(s);
   assertTrue(vector.contains(s));
   vector.remove(s);
   assertFalse(vector.contains(s));
 }