@Test
 public void location_coordinates_can_be_set() {
   Location l = createLocation();
   l.setX(5);
   l.setY(10);
   assertEquals(5, l.x());
   assertEquals(10, l.y());
 }
 @Test
 public void location_coordinates_defaults_to_0_0() {
   Location l = createLocation();
   assertEquals(0, l.x());
   assertEquals(0, l.y());
 }