public function testFormValidationCache()
{
$form = new Form();
$form->setName('user_registration');
$element = (new Input())->setName('test')->setValue('first');
$checkedItemsNum = 0;
$element->addValidator(new CallBackValidator(function ($value) use(&$checkedItemsNum) {
$checkedItemsNum++;
return !empty($value);
}));
$form->setElement($element);
# emulate form submit
$form->handle(new FormData('post', [$form->getUid() => '1', 'test' => '123']));
$this->assertTrue($form->isValid());
$this->assertEquals(1, $checkedItemsNum);
$this->assertTrue($form->isValid());
$this->assertTrue($form->isValid());
$this->assertEquals(1, $checkedItemsNum);
}
