public function testRemoveChild()
 {
     $parent = new Node();
     $child = new Node();
     $parent->addChild($child);
     $parent->removeChild($child->id());
     $this->assertFalse($parent->hasChildren());
 }
 public function testRemoveChildNotExists()
 {
     $parent = new Node();
     $parent->removeChild(1);
     $this->assertFalse($parent->hasChildren());
 }