diff --git a/tests/Unit/InterfaceTypeTest.php b/tests/Unit/InterfaceTypeTest.php
index <HASH>..<HASH> 100644
--- a/tests/Unit/InterfaceTypeTest.php
+++ b/tests/Unit/InterfaceTypeTest.php
@@ -45,6 +45,7 @@ class InterfaceTypeTest extends TestCase
     public function testToType(): void
     {
         $type = new ExampleInterfaceType();
+        /** @var InterfaceType $interfaceType */
         $interfaceType = $type->toType();
 
         $this->assertInstanceOf(InterfaceType::class, $interfaceType);
tests: add typehint for InterfaceType

Repored by phpstan:
Call to an undefined method GraphQL\Type\Definition\Type::getFields()