Fixes code_transformers after the latest analyzer changes

pkg/code_transformers/lib/src/test_harness.dart

Index: pkg/code_transformers/lib/src/test_harness.dart
diff --git a/pkg/code_transformers/lib/src/test_harness.dart b/pkg/code_transformers/lib/src/test_harness.dart
index db5390902d1b53cc4978da332e1d5a2198d23719..e579a5879078d990a32a0e51111184cae3a98793 100644
--- a/pkg/code_transformers/lib/src/test_harness.dart
+++ b/pkg/code_transformers/lib/src/test_harness.dart
@@ -117,7 +117,7 @@ class TestHelper implements PackageProvider {
     }).then((_) {
       // We only check messages when an expectation is provided.
       if (messages == null) return;
-      expect(messages.length, messagesSeen,
+      expect(messagesSeen, messages.length,
           reason: 'less messages than expected');
     });
   }