public function testDelete()
 {
     $root = $this->tree('root_1');
     $this->specify('it should be able to delete nodes with their children', function () use($root) {
         expect('node is deleted', $root->delete())->equals(1);
         expect('no nodes left in the database', Tree::find()->all())->isEmpty();
     });
 }
 /**
  * @test
  */
 public function it_should_delete_nodes_with_their_children()
 {
     $root = $this->tree('root_1');
     expect('node is deleted', $root->delete())->equals(1);
     expect('no nodes left in the database', Tree::find()->all())->isEmpty();
 }