Grouped product frontend quantity validation added and code refactor

app/code/Magento/Catalog/Test/Mftf/Test/AdminAddInStockProductToTheCartTest.xml

@@ -48,7 +48,7 @@
             <argument name="value" value="Yes"/>
         </actionGroup>
         <actionGroup ref="AdminFillAdvancedInventoryQtyActionGroup" stepKey="fillProductQty">
-            <argument name="qty" value="5"/>
+            <argument name="qty" value="8"/>
         </actionGroup>
         <comment userInput="Comment is added to preserve the step key for backward compatibility" stepKey="uncheckMiniQtyCheckBox"/>
         <actionGroup ref="AdminSetMinAllowedQtyForProductActionGroup" stepKey="fillMiniAllowedQty">
@@ -111,17 +111,17 @@
             <argument name="productQty" value="4"/>
         </actionGroup>
         <actionGroup ref="StorefrontAddProductToCartWithQtyActionGroup" stepKey="addAdditionalProductToCart">
-            <argument name="productQty" value="1"/>
+            <argument name="productQty" value="4"/>
         </actionGroup>
         <comment userInput="Comment is added to preserve the step key for backward compatibility" stepKey="seeSuccessSaveMessage"/>
         <seeElement selector="{{StorefrontMinicartSection.quantity(6)}}" stepKey="seeAddedProductQuantityInCart"/>
         <actionGroup ref="StorefrontClickOnMiniCartActionGroup" stepKey="clickOnMiniCart"/>
-        <executeJS function="return {{SimpleProduct.price}} * 5" stepKey="expectedCartSubtotal"/>
+        <executeJS function="return {{SimpleProduct.price}} * 8" stepKey="expectedCartSubtotal"/>
         <actionGroup ref="AssertStorefrontMiniCartItemsActionGroup" stepKey="seeProductNameInMiniCart">
             <argument name="productName" value="{{SimpleProduct.name}}"/>
             <argument name="productPrice" value="{{SimpleProduct.price}}"/>
             <argument name="cartSubtotal" value="{$expectedCartSubtotal}" />
-            <argument name="qty" value="5"/>
+            <argument name="qty" value="8"/>
         </actionGroup>
         <comment userInput="Comment is added to preserve the step key for backward compatibility" stepKey="seeProductPriceInMiniCart"/>
         <comment userInput="Comment is added to preserve the step key for backward compatibility" stepKey="seeCheckOutButtonInMiniCart"/>

app/code/Magento/CatalogInventory/Block/Plugin/ProductView.php

@@ -5,49 +5,42 @@
  */
 namespace Magento\CatalogInventory\Block\Plugin;
 
-use Magento\CatalogInventory\Api\StockRegistryInterface;
+use Magento\Catalog\Block\Product\View;
+use Magento\CatalogInventory\Model\Product\QuantityValidator;
 
 class ProductView
 {
     /**
-     * @var StockRegistryInterface
+     * @var QuantityValidator
      */
-    private $stockRegistry;
+    private $productQuantityValidator;
 
     /**
-     * @param StockRegistryInterface $stockRegistry
+     * @param QuantityValidator $productQuantityValidator
      */
     public function __construct(
-        StockRegistryInterface $stockRegistry
+        QuantityValidator $productQuantityValidator
     ) {
-        $this->stockRegistry = $stockRegistry;
+        $this->productQuantityValidator = $productQuantityValidator;
     }
 
     /**
      * Adds quantities validator.
      *
-     * @param \Magento\Catalog\Block\Product\View $block
+     * @param View $block
      * @param array $validators
      * @return array
      */
     public function afterGetQuantityValidators(
-        \Magento\Catalog\Block\Product\View $block,
+        View $block,
         array $validators
     ) {
-        $stockItem = $this->stockRegistry->getStockItem(
-            $block->getProduct()->getId(),
-            $block->getProduct()->getStore()->getWebsiteId()
+        return array_merge(
+            $validators,
+            $this->productQuantityValidator->getData(
+                $block->getProduct()->getId(),
+                $block->getProduct()->getStore()->getWebsiteId()
+            )
         );
-
-        $params = [];
-        if ($stockItem->getMaxSaleQty()) {
-            $params['maxAllowed'] = (float)$stockItem->getMaxSaleQty();
-        }
-        if ($stockItem->getQtyIncrements() > 0) {
-            $params['qtyIncrements'] = (float)$stockItem->getQtyIncrements();
-        }
-        $validators['validate-item-quantity'] = $params;
-
-        return $validators;
     }
 }

app/code/Magento/CatalogInventory/Model/Product/QuantityValidator.php

@@ -0,0 +1,51 @@
+<?php
+/**
+ * Copyright 2024 Adobe
+ * All Rights Reserved.
+ */
+declare(strict_types=1);
+
+namespace Magento\CatalogInventory\Model\Product;
+
+use Magento\CatalogInventory\Api\StockRegistryInterface;
+
+class QuantityValidator
+{
+    /**
+     * @param StockRegistryInterface $stockRegistry
+     */
+    public function __construct(
+        private readonly StockRegistryInterface $stockRegistry
+    ) {
+    }
+
+    /**
+     * To get quantity validators
+     *
+     * @param int $productId
+     * @param int|null $websiteId
+     *
+     * @return array
+     */
+    public function getData(int $productId, int|null $websiteId): array
+    {
+        $stockItem = $this->stockRegistry->getStockItem($productId, $websiteId);
+
+        if (!$stockItem) {
+            return [];
+        }
+
+        $params = [];
+        $validators = [];
+        $params['minAllowed'] =  $stockItem->getMinSaleQty();
+        if ($stockItem->getMaxSaleQty()) {
+            $params['maxAllowed'] = $stockItem->getMaxSaleQty();
+        }
+        if ($stockItem->getQtyIncrements() > 0) {
+            $params['qtyIncrements'] = (float) $stockItem->getQtyIncrements();
+        }
+        $validators['validate-item-quantity'] = $params;
+
+        return $validators;
+    }
+}

app/code/Magento/CatalogInventory/Test/Unit/Model/Product/QuantityValidatorTest.php

@@ -0,0 +1,132 @@
+<?php
+/**
+ * Copyright 2025 Adobe
+ * All Rights Reserved.
+ */
+declare(strict_types=1);
+
+namespace Magento\CatalogInventory\Test\Unit\Model\Product;
+
+use Magento\CatalogInventory\Api\StockRegistryInterface;
+use Magento\CatalogInventory\Model\Product\QuantityValidator;
+use Magento\CatalogInventory\Api\Data\StockItemInterface;
+use PHPUnit\Framework\MockObject\MockObject;
+use PHPUnit\Framework\TestCase;
+
+/**
+ * @covers \Magento\CatalogInventory\Model\Product\QuantityValidator
+ */
+class QuantityValidatorTest extends TestCase
+{
+    private const PRODUCT_ID = 42;
+    private const WEBSITE_ID = 1;
+
+    /**
+     * @var QuantityValidator
+     */
+    private $quantityValidator;
+
+    /**
+     * @var StockRegistryInterface|MockObject
+     */
+    private $stockRegistry;
+
+    protected function setUp(): void
+    {
+        $this->stockRegistry = $this->createMock(StockRegistryInterface::class);
+
+        $this->quantityValidator = new QuantityValidator(
+            $this->stockRegistry
+        );
+    }
+
+    public function testGetDataWithMinMaxAndIncrements(): void
+    {
+        $stockItem = $this->createMock(StockItemInterface::class);
+
+        $stockItem->method('getMinSaleQty')
+            ->willReturn(2.0);
+
+        $stockItem->method('getMaxSaleQty')
+            ->willReturn(10.0);
+
+        $stockItem->method('getQtyIncrements')
+            ->willReturn(2.0);
+
+        $this->stockRegistry->expects($this->once())
+            ->method('getStockItem')
+            ->with(self::PRODUCT_ID, self::WEBSITE_ID)
+            ->willReturn($stockItem);
+
+        $expected = [
+            'validate-item-quantity' => [
+                'minAllowed' => 2.0,
+                'maxAllowed' => 10.0,
+                'qtyIncrements' => 2.0
+            ]
+        ];
+
+        $result = $this->quantityValidator->getData(self::PRODUCT_ID, self::WEBSITE_ID);
+        $this->assertEquals($expected, $result);
+    }
+
+    public function testReturnsEmptyArrayForNonExistentProductOrWebsite(): void
+    {
+        $this->stockRegistry->expects($this->once())
+            ->method('getStockItem')
+            ->with(self::PRODUCT_ID, self::WEBSITE_ID)
+            ->willReturn(null);
+
+        $result = $this->quantityValidator->getData(self::PRODUCT_ID, self::WEBSITE_ID);
+        $this->assertSame([], $result, 'Should return empty array when StockItem is not found');
+    }
+
+    public function testHandlesNullValuesFromStockItem(): void
+    {
+        $stockItem = $this->createMock(StockItemInterface::class);
+        $stockItem->method('getMinSaleQty')
+            ->willReturn(null);
+        $stockItem->method('getMaxSaleQty')
+            ->willReturn(null);
+        $stockItem->method('getQtyIncrements')
+            ->willReturn(null);
+
+        $this->stockRegistry->expects($this->once())
+            ->method('getStockItem')
+            ->with(self::PRODUCT_ID, self::WEBSITE_ID)
+            ->willReturn($stockItem);
+
+        $expected = [
+            'validate-item-quantity' => [
+                'minAllowed'    => null
+            ],
+        ];
+        $result = $this->quantityValidator->getData(self::PRODUCT_ID, self::WEBSITE_ID);
+        $this->assertEquals($expected, $result);
+    }
+
+    public function testHandlesInvalidValuesFromStockItem(): void
+    {
+        $stockItem = $this->createMock(StockItemInterface::class);
+        $stockItem->method('getMinSaleQty')
+            ->willReturn('not-a-number');
+        $stockItem->method('getMaxSaleQty')
+            ->willReturn(-5);
+        $stockItem->method('getQtyIncrements')
+            ->willReturn(false);
+
+        $this->stockRegistry->expects($this->once())
+            ->method('getStockItem')
+            ->with(self::PRODUCT_ID, self::WEBSITE_ID)
+            ->willReturn($stockItem);
+
+        $expected = [
+            'validate-item-quantity' => [
+                'minAllowed'    => 'not-a-number',
+                'maxAllowed'    => -5
+            ],
+        ];
+        $result = $this->quantityValidator->getData(self::PRODUCT_ID, self::WEBSITE_ID);
+        $this->assertEquals($expected, $result);
+    }
+}