Add explicit test for @enum directive

#2629

tests/Integration/Schema/Directives/EnumDirectiveTest.php

@@ -0,0 +1,40 @@
+<?php declare(strict_types=1);
+
+namespace Tests\Integration\Schema\Directives;
+
+use Tests\TestCase;
+
+final class EnumDirectiveTest extends TestCase
+{
+    public function testDefinesEnumWithInternalValues(): void
+    {
+        $this->mockResolver(function ($_, array $args): string {
+            $this->assertSame('Active internal', $args['status']);
+
+            return 'Not active';
+        });
+
+        $this->schema = /** @lang GraphQL */ '
+        enum Status {
+            ACTIVE @enum(value: "Active internal")
+            INACTIVE @enum(value: "Not active")
+        }
+
+        type Query {
+            status(status: Status!): Status! @mock
+        }
+        ';
+
+        $this
+            ->graphQL(/** @lang GraphQL */ '
+            {
+                status(status: ACTIVE)
+            }
+            ')
+            ->assertExactJson([
+                'data' => [
+                    'status' => 'INACTIVE',
+                ]
+            ]);
+    }
+}