Prevent undefined stdout index error - #3727

(cherry picked from commit 663abe7)

src/Runner/PhptTestCase.php

@@ -177,7 +177,7 @@ public function run(TestResult $result = null): TestResult
         }
 
         try {
-            $this->assertPhptExpectation($sections, $jobResult['stdout']);
+            $this->assertPhptExpectation($sections, $this->output);
         } catch (AssertionFailedError $e) {
             $failure = $e;