@Test
public void isAncestorWorks() throws Exception {

  JPanel panel1 = new JPanel();
  JPanel panel11 = new JPanel();
  JPanel panel12 = new JPanel();
  JPanel panel123 = new JPanel();
  JPanel panel13 = new JPanel();
  panel1.add(panel11);
  panel1.add(panel12);
  panel12.add(panel123);
  panel1.add(panel13);
  assertThat(TreeWalker.isAncestor(panel1, panel123)).isTrue();
  assertThat(TreeWalker.isAncestor(panel123, panel1)).isFalse();
  assertThat(TreeWalker.isAncestor(panel1, panel1)).isTrue();
  assertThat(TreeWalker.isAncestor(panel11, panel123)).isFalse();
  assertThat(TreeWalker.isAncestor(panel12, panel123)).isTrue();
}