Make tests compatible with PHPUnit 8

tests/unit/Foundation/ErrorHandling/ExceptionHandler/ValidationExceptionHandlerTest.php

@@ -17,7 +17,7 @@ class ValidationExceptionHandlerTest extends TestCase
 {
     private $handler;
 
-    public function setUp()
+    protected function setUp(): void
     {
         $this->handler = new ValidationExceptionHandler;
     }