@Test
 public void isNotCorrectPlane() {
   Plane plane = new Plane(0, 0, 0, 1);
   assertFalse(plane.isCorrect());
 }
 @Test
 public void isCorrectPlane() {
   Plane plane = new Plane(0, 0, 0, 0);
   assertTrue(plane.isCorrect());
 }