public function testGetAliases()
 {
     $this->rawLayoutBuilder->add('root', null, 'root')->add('header', 'root', 'header')->addAlias('root_alias1', 'root')->addAlias('root_alias2', 'root_alias1');
     $this->assertEquals(['root_alias1', 'root_alias2'], $this->rawLayoutBuilder->getAliases('root'));
     $this->assertEquals([], $this->rawLayoutBuilder->getAliases('root_alias1'));
     $this->assertEquals([], $this->rawLayoutBuilder->getAliases('root_alias2'));
     $this->assertEquals([], $this->rawLayoutBuilder->getAliases('header'));
     $this->assertEquals([], $this->rawLayoutBuilder->getAliases('unknown'));
 }