Update test/parallel/test-esm-loader-null-source.js

Co-authored-by: Antoine du Hamel <duhamelantoine1995@gmail.com>

Author: vivek958

test/parallel/test-esm-loader-null-source.js

@@ -41,9 +41,9 @@ const fixtures = require('../common/fixtures');
   const output = result.stdout + result.stderr;
 
   // Verify test passed
-  assert.ok(
-    output.includes('PASS: Got expected error'),
-    'Should pass with expected error. Output: ' + output
+  assert.match(
+    output,
+    /PASS: Got expected error/,
   );
 
   assert.strictEqual(