ENGCOM-6591: magento/magento2#: Unit test for \Magento\Review\Observer\CatalogProductListCollectionAppendSummaryFieldsObserver #26312

 - Merge Pull Request #26312 from atwixfirster/magento2:unittest-CatalogProductListCollectionAppendSummaryFieldsObserver
 - Merged commits:
   1. 7cb90f2
   2. 548e0cc
   3. 1b3101d

Author: magento-engcom-team

app/code/Magento/Review/Test/Unit/Observer/CatalogProductListCollectionAppendSummaryFieldsObserverTest.php

@@ -0,0 +1,149 @@
+<?php
+/**
+ * Copyright © Magento, Inc. All rights reserved.
+ * See COPYING.txt for license details.
+ */
+declare(strict_types = 1);
+
+namespace Magento\Review\Test\Unit\Observer;
+
+use Magento\CatalogSearch\Model\ResourceModel\Fulltext\Collection;
+use Magento\Framework\Event;
+use Magento\Framework\Event\Observer;
+use Magento\Review\Model\ResourceModel\Review\Summary;
+use Magento\Review\Model\ResourceModel\Review\SummaryFactory;
+use Magento\Review\Observer\CatalogProductListCollectionAppendSummaryFieldsObserver;
+use Magento\Store\Api\Data\StoreInterface;
+use Magento\Store\Model\StoreManagerInterface;
+use MockObject;
+use PHPUnit\Framework\TestCase;
+
+/**
+ * Test class for \Magento\Review\Observer\CatalogProductListCollectionAppendSummaryFieldsObserver
+ */
+class CatalogProductListCollectionAppendSummaryFieldsObserverTest extends TestCase
+{
+    private const STORE_ID = '1';
+
+    /**
+     * @var Event|MockObject
+     */
+    private $eventMock;
+
+    /**
+     * Testable Object
+     *
+     * @var CatalogProductListCollectionAppendSummaryFieldsObserver
+     */
+    private $observer;
+
+    /**
+     * @var Observer|MockObject
+     */
+    private $observerMock;
+
+    /**
+     * @var Collection|MockObject
+     */
+    private $productCollectionMock;
+
+    /**
+     * @var StoreInterface|MockObject
+     */
+    private $storeMock;
+
+    /**
+     * @var StoreManagerInterface|MockObject
+     */
+    private $storeManagerMock;
+
+    /**
+     * @var Summary|MockObject
+     */
+    private $sumResourceMock;
+
+    /**
+     * @var SummaryFactory|MockObject
+     */
+    private $sumResourceFactoryMock;
+
+    /**
+     * @inheritdoc
+     */
+    protected function setUp() : void
+    {
+        $this->eventMock = $this->getMockBuilder(Event::class)
+            ->disableOriginalConstructor()
+            ->setMethods(['getCollection'])
+            ->getMock();
+
+        $this->observerMock = $this->createMock(Observer::class);
+
+        $this->productCollectionMock = $this->getMockBuilder(Collection::class)
+            ->disableOriginalConstructor()
+            ->getMock();
+
+        $this->storeManagerMock = $this->getMockBuilder(StoreManagerInterface::class)
+            ->disableOriginalConstructor()
+            ->setMethods(['getStore'])
+            ->getMockForAbstractClass();
+
+        $this->storeMock = $this->getMockBuilder(StoreInterface::class)
+            ->disableOriginalConstructor()
+            ->setMethods(['getId'])
+            ->getMockForAbstractClass();
+
+        $this->sumResourceMock = $this->createPartialMock(
+            Summary::class,
+            ['appendSummaryFieldsToCollection']
+        );
+
+        $this->sumResourceFactoryMock = $this->getMockBuilder(SummaryFactory::class)
+            ->disableOriginalConstructor()
+            ->setMethods(['create'])
+            ->getMock();
+
+        $this->observer = new CatalogProductListCollectionAppendSummaryFieldsObserver(
+            $this->sumResourceFactoryMock,
+            $this->storeManagerMock
+        );
+    }
+
+    /**
+     * Product listing test
+     */
+    public function testAddSummaryFieldToProductsCollection() : void
+    {
+        $this->eventMock
+            ->expects($this->once())
+            ->method('getCollection')
+            ->willReturn($this->productCollectionMock);
+
+        $this->observerMock
+            ->expects($this->once())
+            ->method('getEvent')
+            ->willReturn($this->eventMock);
+
+        $this->storeManagerMock
+            ->expects($this->once())
+            ->method('getStore')
+            ->willReturn($this->storeMock);
+
+        $this->storeMock
+            ->expects($this->once())
+            ->method('getId')
+            ->willReturn(self::STORE_ID);
+
+        $this->sumResourceFactoryMock
+            ->expects($this->once())
+            ->method('create')
+            ->willReturn($this->sumResourceMock);
+
+        $this->sumResourceMock
+            ->expects($this->once())
+            ->method('appendSummaryFieldsToCollection')
+            ->willReturn($this->sumResourceMock);
+
+        $this->observer->execute($this->observerMock);
+    }
+}