@Test
public void setChild() throws Exception {

  fce.setChild(0, arg4);
  fce.setChild(1, arg3);
  fce.setChild(2, arg2);
  fce.setChild(3, arg1);
  assertEquals(arg4, fce.getArg(0));
  assertEquals(arg3, fce.getArg(1));
  assertEquals(arg2, fce.getArg(2));
  assertEquals(arg1, fce.getArg(3));
}