Add test for multiple schema's with custom int type

tests/MultipleSchemaTest.php

@@ -0,0 +1,53 @@
+<?php declare(strict_types=1);
+
+namespace GraphQL\Tests;
+
+use GraphQL\Executor\Promise\Adapter\SyncPromiseAdapter;
+use GraphQL\Executor\Promise\Promise;
+use GraphQL\GraphQL;
+use GraphQL\Type\Definition\ObjectType;
+use GraphQL\Type\Definition\Type;
+use GraphQL\Type\Registry\DefaultStandardTypeRegistry;
+use GraphQL\Type\Schema;
+use GraphQL\Type\SchemaConfig;
+use PHPUnit\Framework\TestCase;
+
+final class MultipleSchemaTest extends TestCase
+{
+    public function testMultipleSchemasWithCustomIntType(): void
+    {
+        $schema1 = $this->createSchema();
+        $result1 = GraphQL::executeQuery($schema1, '{ count }');
+        self::assertSame(['data' => ['count' => 1]], $result1->toArray());
+
+        $schema2 = $this->createSchema();
+        $result2 = GraphQL::executeQuery($schema2, '{ count }');
+        self::assertSame(['data' => ['count' => 1]], $result2->toArray());
+
+        self::assertNotSame($schema1->getType('Int'), $schema2->getType('Int'));
+    }
+
+    private function createSchema() : Schema
+    {
+        $typeRegistry = new DefaultStandardTypeRegistry(
+            CustomIntType::class
+        );
+
+        $query = new ObjectType([
+            'name' => 'Query',
+            'fields' => [
+                'count' => [
+                    'type' => Type::nonNull($typeRegistry->int()),
+                    'resolve' => fn() => 1,
+                ],
+            ],
+        ]);
+
+        $config = SchemaConfig::create([
+            'typeRegistry' => $typeRegistry,
+            'query' => $query,
+        ]);
+
+        return  new Schema($config) ;
+    }
+}