Merge pull request #217 from php-school/AydinHassan-patch-1

Add void type

Author: AydinHassan

src/TestUtils/WorkshopExerciseTest.php

@@ -60,7 +60,7 @@ private function getExercise(): ExerciseInterface
             ->findByClassName($this->getExerciseClass());
     }
 
-    public function runExercise(string $submissionFile)
+    public function runExercise(string $submissionFile): void
     {
         $exercise = $this->getExercise();