migrate test cases to use pestphp syntax

tests/Unit/Entity/FoodOrderTest.php

@@ -0,0 +1,32 @@
+<?php declare(strict_types=1);
+
+namespace App\Tests\Unit\Entity;
+
+use App\Entity\FoodOrder;
+use App\Entity\OrderItem;
+
+use function expect;
+use function test;
+
+test('FoodOrder Entity', function (): void {
+    $order = new FoodOrder;
+    $orderItem = new OrderItem;
+    expect($order->getOrderItems())
+        ->toBeEmpty();
+    $order->addOrderItem($orderItem);
+    $order->addOrderItem($orderItem);
+
+    expect($order->getOrderItems())
+        ->toHaveCount(1)
+        ->and($orderItem->getFoodOrder())
+        ->toBe($order);
+
+    $order->removeOrderItem($orderItem);
+
+    expect($order->getOrderItems())
+        ->toBeEmpty()
+        ->and($orderItem->getFoodOrder())
+        ->toBeNull();
+
+})
+    ->covers(FoodOrder::class, OrderItem::class);