@Test
public void testAdd() {

  final Vector3 vec1 = new Vector3();
  final Vector3 vec2 = new Vector3(Vector3.ONE);
  vec1.addLocal(1, 2, 3);
  assertEquals(new Vector3(1, 2, 3), vec1);
  vec1.addLocal(-1, -2, -3);
  assertEquals(Vector3.ZERO, vec1);
  vec1.zero();
  vec1.addLocal(vec2);
  assertEquals(Vector3.ONE, vec1);
  vec1.zero();
  final Vector3 vec3 = vec1.add(vec2, new Vector3());
  assertEquals(Vector3.ZERO, vec1);
  assertEquals(Vector3.ONE, vec3);
  final Vector3 vec4 = vec1.add(1, 0, 0, null);
  assertEquals(Vector3.ZERO, vec1);
  assertEquals(Vector3.UNIT_X, vec4);
}