public function testAddHintCustomTreeWalkerWithExistingAnotherWalker()
 {
     $query = $this->getQuery();
     $query->setHint(Query::HINT_CUSTOM_TREE_WALKERS, ['another_walker_class']);
     $added = $this->queryHintResolver->addHint($query, Query::HINT_CUSTOM_TREE_WALKERS, 'walker_class');
     $this->assertTrue($added);
     $this->assertEquals([Query::HINT_CUSTOM_TREE_WALKERS => ['another_walker_class', 'walker_class']], $query->getHints());
 }