@Test
public void testAdd() {

  final Vector4 vec1 = new Vector4();
  final Vector4 vec2 = new Vector4(Vector4.ONE);
  vec1.addLocal(1, 2, 3, 4);
  assertEquals(new Vector4(1, 2, 3, 4), vec1);
  vec1.addLocal(-1, -2, -3, -4);
  assertEquals(Vector4.ZERO, vec1);
  vec1.zero();
  vec1.addLocal(vec2);
  assertEquals(Vector4.ONE, vec1);
  vec1.zero();
  final Vector4 vec3 = vec1.add(vec2, new Vector4());
  assertEquals(Vector4.ZERO, vec1);
  assertEquals(Vector4.ONE, vec3);
  final Vector4 vec4 = vec1.add(0, 0, 0, 1, null);
  assertEquals(Vector4.ZERO, vec1);
  assertEquals(Vector4.UNIT_W, vec4);
}