@Test
public void testSimpleHash() {

  // Just a simple sanity check.
  final Ring ring1 = new Ring(Vector3.ZERO, Vector3.UNIT_Y, 0.0, 2.0);
  final Ring ring2 = new Ring(Vector3.ZERO, Vector3.UNIT_Y, 0.0, 2.0);
  final Ring ring3 = new Ring(Vector3.ZERO, Vector3.UNIT_Y, 0.0, 3.0);
  assertTrue(ring1.hashCode() == ring2.hashCode());
  assertTrue(ring1.hashCode() != ring3.hashCode());
}