@Test
public void testLookAt() {

  final Vector3 direction = new Vector3(-1, 0, 0);
  final Matrix3 mat3 = new Matrix3().lookAt(direction, Vector3.UNIT_Y);
  assertEquals(direction, mat3.applyPost(Vector3.UNIT_Z, null));
  direction.set(1, 1, 1).normalizeLocal();
  mat3.lookAt(direction, Vector3.UNIT_Y);
  assertEquals(direction, mat3.applyPost(Vector3.UNIT_Z, null));
  direction.set(-1, 2, -1).normalizeLocal();
  mat3.lookAt(direction, Vector3.UNIT_Y);
  assertEquals(direction, mat3.applyPost(Vector3.UNIT_Z, new Vector3()));
}