ENGCOM-6960: Unit test for AssignCouponDataAfterOrderCustomerAssignObserver #26947

 - Merge Pull Request #26947 from mmezhensky/magento2:unittest-AssignCouponDataAfterOrderCustomerAssignObserverTest
 - Merged commits:
   1. 83e5938
   2. 1e8ca39

Author: magento-engcom-team

app/code/Magento/SalesRule/Test/Unit/Observer/AssignCouponDataAfterOrderCustomerAssignObserverTest.php

@@ -0,0 +1,150 @@
+<?php
+/**
+ * Copyright © Magento, Inc. All rights reserved.
+ * See COPYING.txt for license details.
+ */
+
+declare(strict_types=1);
+
+namespace Magento\SalesRule\Test\Unit\Observer;
+
+use Magento\Framework\Event;
+use Magento\Framework\Event\Observer;
+use Magento\Framework\TestFramework\Unit\Helper\ObjectManager;
+use Magento\Sales\Api\Data\OrderInterface;
+use Magento\SalesRule\Model\Coupon\UpdateCouponUsages;
+use Magento\SalesRule\Observer\AssignCouponDataAfterOrderCustomerAssignObserver;
+use PHPUnit\Framework\MockObject\MockObject;
+use PHPUnit\Framework\TestCase;
+
+/**
+ * Unit test for Magento\SalesRule\Observer\AssignCouponDataAfterOrderCustomerAssignObserver
+ */
+class AssignCouponDataAfterOrderCustomerAssignObserverTest extends TestCase
+{
+    /*
+     * Stub event key order
+     */
+    private const STUB_EVENT_KEY_ORDER = 'order';
+
+    /*
+     * Stub customer ID
+     */
+    private const STUB_CUSTOMER_ID = 1;
+
+    /**
+     * Testable Object
+     *
+     * @var AssignCouponDataAfterOrderCustomerAssignObserver
+     */
+    private $observer;
+
+    /**
+     * @var ObjectManager
+     */
+    private $objectManager;
+
+    /**
+     * @var Observer|MockObject
+     */
+    private $observerMock;
+
+    /**
+     * @var Event|MockObject
+     */
+    private $eventMock;
+
+    /**
+     * @var OrderInterface|MockObject
+     */
+    private $orderMock;
+
+    /**
+     * @var UpdateCouponUsages|MockObject
+     */
+    private $updateCouponUsagesMock;
+
+    protected function setUp(): void
+    {
+        $this->objectManager = new ObjectManager($this);
+        $this->observerMock = $this->createMock(Observer::class);
+
+        $this->eventMock = $this->getMockBuilder(Event::class)
+            ->disableOriginalConstructor()
+            ->setMethods(['getData'])
+            ->getMock();
+
+        $this->orderMock = $this->getMockBuilder(OrderInterface::class)
+            ->disableOriginalConstructor()
+            ->getMock();
+
+        $this->updateCouponUsagesMock = $this->getMockBuilder(UpdateCouponUsages::class)
+            ->disableOriginalConstructor()
+            ->setMethods(['execute'])
+            ->getMock();
+
+        $this->observer = $this->objectManager->getObject(
+            AssignCouponDataAfterOrderCustomerAssignObserver::class,
+            [
+                'updateCouponUsages' => $this->updateCouponUsagesMock
+            ]
+        );
+    }
+
+    /**
+     * Test for execute(), covers test case for assign coupon data after order customer
+     */
+    public function testExecuteAssignCouponData(): void
+    {
+        $this->observerMock
+            ->expects($this->once())
+            ->method('getEvent')
+            ->willReturn($this->eventMock);
+
+        $this->eventMock
+            ->expects($this->once())
+            ->method('getData')
+            ->with(self::STUB_EVENT_KEY_ORDER)
+            ->willReturn($this->orderMock);
+
+        $this->orderMock
+            ->expects($this->once())
+            ->method('getCustomerId')
+            ->willReturn(self::STUB_CUSTOMER_ID);
+
+        $this->updateCouponUsagesMock
+            ->expects($this->once())
+            ->method('execute')
+            ->with($this->orderMock, true);
+
+        $this->observer->execute($this->observerMock);
+    }
+
+    /**
+     * Test for execute(), covers test case for assign coupon data after order customer with empty customer ID
+     */
+    public function testExecuteAssignCouponDataWithEmptyCustomerId(): void
+    {
+        $this->observerMock
+            ->expects($this->once())
+            ->method('getEvent')
+            ->willReturn($this->eventMock);
+
+        $this->eventMock
+            ->expects($this->once())
+            ->method('getData')
+            ->with(self::STUB_EVENT_KEY_ORDER)
+            ->willReturn($this->orderMock);
+
+        $this->orderMock
+            ->expects($this->once())
+            ->method('getCustomerId')
+            ->willReturn(null);
+
+        $this->updateCouponUsagesMock
+            ->expects($this->never())
+            ->method('execute');
+
+        $this->observer->execute($this->observerMock);
+    }
+}