ACP2E-2129: customer is reporting their table rates are not updating via CSV any longer

- added unit tests

Author: aplapana

app/code/Magento/OfflineShipping/Model/ResourceModel/Carrier/Tablerate.php

@@ -298,16 +298,19 @@ public function uploadAndImport(\Magento\Framework\DataObject $object)
         } else {
             $request = $this->requestFactory->create();
             $files = (array)$request->getFiles();
+
             if (empty($files['groups']['tablerate']['fields']['import']['value'])) {
                 return $this;
             } else {
                 $filePath = $files['groups']['tablerate']['fields']['import']['value']['tmp_name'];
             }
         }
+        if (!$filePath) {
+            return $this;
+        }
 
         $websiteId = $this->storeManager->getWebsite($object->getScopeId())->getId();
         $conditionName = $this->getConditionName($object);
-
         $file = $this->getCsvFile($filePath);
         try {
             // delete old data by website and condition name

app/code/Magento/OfflineShipping/Test/Unit/Model/ResourceModel/Carrier/TablerateTest.php

@@ -11,7 +11,6 @@
 use Magento\Framework\App\DeploymentConfig;
 use Magento\Framework\App\Request\Http;
 use Magento\Framework\App\RequestFactory;
-use Magento\Framework\App\RequestInterface;
 use Magento\Framework\App\ResourceConnection;
 use Magento\Framework\DB\Adapter\AdapterInterface;
 use Magento\Framework\Filesystem;