ACP2E-2990: Customer "created_at" date Not Converted to store time zone upon export

 - Added the test coverage.

Author: devarul

app/code/Magento/CustomerImportExport/Test/Unit/Plugin/Model/Export/FormatCustomerCreatedAtTest.php

@@ -0,0 +1,67 @@
+<?php
+/************************************************************************
+ * Copyright 2024 Adobe
+ * All Rights Reserved.
+ *
+ * NOTICE: All information contained herein is, and remains
+ * the property of Adobe and its suppliers, if any. The intellectual
+ * and technical concepts contained herein are proprietary to Adobe
+ * and its suppliers and are protected by all applicable intellectual
+ * property laws, including trade secret and copyright laws.
+ * Dissemination of this information or reproduction of this material
+ * is strictly forbidden unless prior written permission is obtained
+ * from Adobe.
+ * ***********************************************************************
+ */
+declare(strict_types=1);
+
+namespace Magento\CustomerImportExport\Test\Unit\Plugin\Model\Export;
+
+use Magento\CustomerImportExport\Plugin\Model\Export\FormatCustomerCreatedAt;
+use Magento\Framework\Stdlib\DateTime\TimezoneInterface;
+use PHPUnit\Framework\MockObject\MockObject;
+use Magento\CustomerImportExport\Model\Export\Customer;
+use Magento\Customer\Model\Customer as Item;
+use PHPUnit\Framework\TestCase;
+
+class FormatCustomerCreatedAtTest extends TestCase
+{
+    /**
+     * @var Customer|MockObject
+     */
+    private $subjectMock;
+
+    /**
+     * @var Item|MockObject
+     */
+    private $itemMock;
+
+    /**
+     * Format customer createdAt plugin model
+     *
+     * @var FormatCustomerCreatedAt
+     */
+    private $model;
+
+    protected function setUp(): void
+    {
+        $timeZone = $this->getMockForAbstractClass(TimezoneInterface::class);
+        $this->subjectMock = $this->getMockBuilder(Customer::class)
+            ->disableOriginalConstructor()
+            ->getMock();
+        $this->itemMock = $this->getMockBuilder(Item::class)
+            ->disableOriginalConstructor()
+            ->getMock();
+        $this->model = new FormatCustomerCreatedAt(
+            $timeZone
+        );
+    }
+
+    public function testBeforeExportIte()
+    {
+        $this->model->beforeExportItem(
+            $this->subjectMock,
+            $this->itemMock
+        );
+    }
+}