### Question:
BackButtonHelper { public void addToPushedChild(ViewController child) { if (child.options.topBar.buttons.left != null || child.options.topBar.buttons.back.visible.isFalse()) return; Options options = new Options(); options.topBar.buttons.back.setVisible(); child.mergeOptions(options); }  void addToPushedChild(ViewController child); void clear(ViewController child);  }### Answer:
@Test public void addToChild() { uut.addToPushedChild(child1); verify(child1).mergeOptions(any()); }