public function testRoots()
 {
     $this->assertEquals([1], array_map(function ($value) {
         return $value->id;
     }, Node::find()->roots()->all()));
     $this->assertEquals([1, 26], array_map(function ($value) {
         return $value->id;
     }, MultipleTreeNode::find()->roots()->all()));
 }
 public function testOptimize()
 {
     Node::findOne(6)->optimize();
     MultipleTreeNode::findOne(9)->optimize();
     $dataSet = $this->getConnection()->createDataSet(['tree', 'multiple_tree']);
     $expectedDataSet = new ArrayDataSet(require __DIR__ . '/data/test-optimize.php');
     $this->assertDataSetsEqual($expectedDataSet, $dataSet);
 }