/**
  * Verify displayed product special price on product page(front-end) equals passed from fixture
  *
  * @return string|null
  */
 protected function verifySpecialPrice()
 {
     if (!$this->product->hasData('special_price')) {
         return null;
     }
     $fixtureProductSpecialPrice = $this->product->getSpecialPrice();
     $fixtureProductSpecialPrice = number_format($fixtureProductSpecialPrice, 2);
     $formProductSpecialPrice = $this->productView->getPriceBlock()->getSpecialPrice();
     if ($fixtureProductSpecialPrice == $formProductSpecialPrice) {
         return null;
     }
     return "Displayed product special price on product page(front-end) not equals passed from fixture. " . "Actual: {$formProductSpecialPrice}, expected: {$fixtureProductSpecialPrice}.";
 }