First look at modern-spec serializer/deserializer for items

this is not yet used by anything

tests/phpunit/data/bedrock/item/ItemSerializerDeserializerTest.php

@@ -0,0 +1,66 @@
+<?php
+
+/*
+ *
+ *  ____            _        _   __  __ _                  __  __ ____
+ * |  _ \ ___   ___| | _____| |_|  \/  (_)_ __   ___      |  \/  |  _ \
+ * | |_) / _ \ / __| |/ / _ \ __| |\/| | | '_ \ / _ \_____| |\/| | |_) |
+ * |  __/ (_) | (__|   <  __/ |_| |  | | | | | |  __/_____| |  | |  __/
+ * |_|   \___/ \___|_|\_\___|\__|_|  |_|_|_| |_|\___|     |_|  |_|_|
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * @author PocketMine Team
+ * @link http://www.pocketmine.net/
+ *
+ *
+*/
+
+declare(strict_types=1);
+
+namespace pocketmine\data\bedrock\item;
+
+use PHPUnit\Framework\TestCase;
+use pocketmine\block\VanillaBlocks;
+use pocketmine\item\VanillaItems;
+
+final class ItemSerializerDeserializerTest extends TestCase{
+
+	private ItemDeserializer $deserializer;
+	private ItemSerializer $serializer;
+
+	public function setUp() : void{
+		$this->deserializer = new ItemDeserializer();
+		$this->serializer = new ItemSerializer();
+	}
+
+	public function testAllVanillaItemsSerializableAndDeserializable() : void{
+		foreach(VanillaItems::getAll() as $item){
+			if($item->isNull()){
+				continue;
+			}
+
+			$itemData = $this->serializer->serialize($item);
+			$newItem = $this->deserializer->deserialize($itemData);
+
+			self::assertTrue($item->equalsExact($newItem));
+		}
+	}
+
+	public function testAllVanillaBlocksSerializableAndDeserializable() : void{
+		foreach(VanillaBlocks::getAll() as $block){
+			$item = $block->asItem();
+			if($item->isNull()){
+				continue;
+			}
+
+			$itemData = $this->serializer->serialize($item);
+			$newItem = $this->deserializer->deserialize($itemData);
+
+			self::assertTrue($item->equalsExact($newItem));
+		}
+	}
+}