MAGETWO-39814: [GITHUB] Improve \Magento\Framework\Api\SortOrder #1422

 - Fixed code style and static tests

app/code/Magento/Quote/Model/QuoteRepository.php

@@ -14,6 +14,11 @@
 use Magento\Framework\Exception\InputException;
 use Magento\Framework\Api\ExtensionAttribute\JoinProcessorInterface;
 
+/**
+ * Class QuoteRepository
+ *
+ * @SuppressWarnings(PHPMD.CouplingBetweenObjects)
+ */
 class QuoteRepository implements \Magento\Quote\Api\CartRepositoryInterface
 {
     /**

app/code/Magento/Tax/Test/Unit/Model/TaxRuleRepositoryTest.php

@@ -8,7 +8,6 @@
 use Magento\Framework\Api\SortOrder;
 use \Magento\Tax\Model\TaxRuleRepository;
 
-
 class TaxRuleRepositoryTest extends \PHPUnit_Framework_TestCase
 {
     /**

lib/internal/Magento/Framework/Api/SortOrder.php

@@ -19,6 +19,11 @@ class SortOrder extends AbstractSimpleObject
     const SORT_ASC = 'ASC';
     const SORT_DESC = 'DESC';
 
+    /**
+     * Initialize object and validate sort direction
+     *
+     * @param array $data
+     */
     public function __construct(array $data = [])
     {
         parent::__construct($data);
@@ -75,7 +80,7 @@ public function setDirection($direction)
      * Validate direction argument ASC or DESC
      * 
      * @param mixed $direction
-     * @return string
+     * @return null
      * @throws InputException
      */
     private function validateDirection($direction)
@@ -87,6 +92,7 @@ private function validateDirection($direction)
     /**
      * @param string $direction
      * @throws InputException
+     * @return null
      */
     private function validateDirectionIsString($direction)
     {
@@ -101,6 +107,7 @@ private function validateDirectionIsString($direction)
     /**
      * @param string $direction
      * @throws InputException
+     * @return null
      */
     private function validateDirectionIsAscOrDesc($direction)
     {