anchor.diff:    for (var entry in sortedExceptions) {
       print('  ${entry.key} (x${entry.value.length})');
     }
  +
  +  if (categoryOfInterest == null) {
  +    print('\n(Note: to show stack traces & nodes for a particular failure,'
  +        ' rerun with a search string as an argument.)');
  +  }
   }
   
  -/// Set this to a non-null value to cause any exception to be printed in full
  -/// if its category contains the string.
  -const String categoryOfInterest = null;
  +void warnOnNoAssertions() {
  +  try {
  +    assert(false);
  +  } catch (e) {
  +    return;
  +  }
   
  -/// Set this to `true` to cause just the exception nodes to be printed when
  -/// `categoryOfInterest` is non-null.  Set this to `false` to cause the full
  -/// stack trace to be printed.
  -const bool printExceptionNodeOnly = false;
  +  print('''
  +!!!
  +!!! Warning! You didn't --enable-asserts!
  +!!!
  +''');
  +}
   
   class _Listener implements NullabilityMigrationListener {
  +  /// Set this to `true` to cause just the exception nodes to be printed when
  +  /// `_Listener.categoryOfInterest` is non-null.  Set this to `false` to cause
  +  /// the full stack trace to be printed.
  +  /// TODO(mfairhurst): make this a cli flag?
  +  static const bool printExceptionNodeOnly = false;
  +
  +  /// Set this to a non-null value to cause any exception to be printed in full
  +  /// if its category contains the string.
  +  final String categoryOfInterest;
  +
     final groupedExceptions = <String, List<String>>{};
   
     int numExceptions = 0;
  
positive.code: import 'package:analyzer_plugin/protocol/protocol_common.dart';
  import 'package:nnbd_migration/nnbd_migration.dart';
  
  main() async {
    var rootUri = Platform.script.resolve('../../..');
    var listener = _Listener();
    for (var testPath in [
      'third_party/pkg/charcode',
      'third_party/pkg/collection',
  
negative.code:   int numRequiredAnnotationsAdded = 0;
  
    int numDeadCodeSegmentsFound = 0;
  
    _Listener(this.categoryOfInterest);
  
    @override
    void addEdit(SingleNullabilityFix fix, SourceEdit edit) {
  