public function testFieldNarrowing()
 {
     $structure = $this->prophesize(Structure::class)->reveal();
     $available_locales = ['ab', 'cd', 'ef'];
     $context = new QueryContext($structure, $available_locales, 'fr');
     $narrowed = $context->narrowToFields(['some_field']);
     $this->assertEquals(['some_field'], $narrowed->getFields());
 }
 public function buildQuery(QueryContext $context)
 {
     $fields = array($this->field->getValue());
     return $this->expression->buildQuery($context->narrowToFields($fields));
 }