@Test
public void testSimpleHash() {

  // Just a simple sanity check.
  final Plane plane1 = new Plane(Vector3.UNIT_Y, 2);
  final Plane plane2 = new Plane(Vector3.UNIT_Y, 2);
  final Plane plane3 = new Plane(Vector3.UNIT_Z, 2);
  assertTrue(plane1.hashCode() == plane2.hashCode());
  assertTrue(plane1.hashCode() != plane3.hashCode());
}