ACP2E-1419: [Magento Cloud] - Error image in phtml for back to stock email

 - Added the test coverage and fixed the static test failure.

Author: devarul

app/code/Magento/ProductAlert/Model/Mailing/AlertProcessor.php

@@ -31,7 +31,9 @@
 /**
  * Class for mailing Product Alerts
  *
+ * @SuppressWarnings(PHPMD.ExcessiveParameterList)
  * @SuppressWarnings(PHPMD.CouplingBetweenObjects)
+ * @SuppressWarnings(PHPMD.CyclomaticComplexity)
  */
 class AlertProcessor
 {
@@ -99,7 +101,6 @@ class AlertProcessor
      * @param StoreManagerInterface $storeManager
      * @param ErrorEmailSender $errorEmailSender
      * @param DesignInterface|null $design
-     * @SuppressWarnings(PHPMD.CyclomaticComplexity)
      */
     public function __construct(
         EmailFactory $emailFactory,

dev/tests/integration/testsuite/Magento/ProductAlert/Model/Mailing/AlertProcessorTest.php

@@ -9,13 +9,15 @@
 
 use Magento\Customer\Api\AccountManagementInterface;
 use Magento\Customer\Model\Session;
-use Magento\Framework\App\Area;
 use Magento\Framework\Locale\Resolver;
+use Magento\Framework\Mail\EmailMessage;
 use Magento\Framework\Module\Dir\Reader;
 use Magento\Framework\Phrase;
 use Magento\Framework\Phrase\Renderer\Translate as PhraseRendererTranslate;
 use Magento\Framework\Phrase\RendererInterface;
 use Magento\Framework\Translate;
+use Magento\Framework\View\Design\ThemeInterface;
+use Magento\Framework\View\DesignInterface;
 use Magento\Store\Model\StoreRepository;
 use Magento\TestFramework\Helper\Bootstrap;
 use Magento\TestFramework\Mail\Template\TransportBuilderMock;
@@ -50,6 +52,11 @@ class AlertProcessorTest extends TestCase
      */
     private $transportBuilder;
 
+    /**
+     * @var DesignInterface
+     */
+    private $design;
+
     /**
      * @inheritDoc
      */
@@ -64,6 +71,7 @@ protected function setUp(): void
         $customer = $service->authenticate('customer@example.com', 'password');
         $customerSession = $this->objectManager->get(Session::class);
         $customerSession->setCustomerDataAsLoggedIn($customer);
+        $this->design = $this->objectManager->get(DesignInterface::class);
     }
 
     /**
@@ -139,4 +147,44 @@ private function processAlerts(): void
         $this->publisher->execute($alertType, [$customerId], $websiteId);
         $this->alertProcessor->process($alertType, [$customerId], $websiteId);
     }
+
+    /**
+     * Validate the current theme
+     *
+     * @magentoConfigFixture current_store catalog/productalert/allow_price 1
+     * @magentoDataFixture Magento/ProductAlert/_files/product_alert.php
+     */
+    public function testValidateCurrentTheme()
+    {
+        $this->design->setDesignTheme(
+            $this->objectManager->get(ThemeInterface::class)
+        );
+
+        $this->processAlerts();
+
+        $message = $this->transportBuilder->getSentMessage();
+        $messageContent = $this->getMessageRawContent($message);
+        $emailDom = new \DOMDocument();
+        $emailDom->loadHTML($messageContent);
+
+        $emailXpath = new \DOMXPath($emailDom);
+        $greeting = $emailXpath->query('//img[@class="photo image"]');
+        $this->assertStringContainsString(
+            'thumbnail.jpg',
+            $greeting->item(0)->getAttribute('src')
+        );
+        $this->assertEquals('Magento/luma', $this->design->getDesignTheme()->getCode());
+    }
+
+    /**
+     * Returns raw content of provided message
+     *
+     * @param EmailMessage $message
+     * @return string
+     */
+    private function getMessageRawContent(EmailMessage $message): string
+    {
+        $emailParts = $message->getBody()->getParts();
+        return current($emailParts)->getRawContent();
+    }
 }