anchor.diff:      await driver.waitForSetWithUri(uriStr);
     }
   
  -  Future<void> addTestFile(String content, {int offset}) async {
  +  Future<List<CompletionSuggestion>> addTestFile(String content,
  +      {int offset}) async {
       driver.addTestFile(content, offset: offset);
       await getSuggestions();
  +    // For sanity, ensure that there are no errors recorded for project files
  +    // since that may lead to unexpected results.
  +    _assertNoErrorsInProjectFiles();
  +    return suggestions;
     }
   
     void expectNoSuggestion({
  
positive.code:   @override
    String get testFilePath => '$projectPath/lib/test.dart';
  
    void assertNoErrorsInCode() {
      var errors = <AnalysisError>[];
      driver.filesErrors.forEach((_, fileErrors) {
        errors.addAll(fileErrors);
      });
      expect(errors, isEmpty);
    }
  
    Future<void> test_project_lib() async {
      await addProjectFile('lib/a.dart', r'''
  class A {}
  
negative.code:   ^
  }
  ''');
  
      expectSuggestion(
          completion: 'A',
  