anchor.diff:  
     test_invalidSelection() async {
       await resolveTestUnit('');
  -    List<Assist> assists = await computeAssists(plugin, context,
  -        resolutionMap.elementDeclaredByCompilationUnit(testUnit).source, -1, 0);
  +    offset = -1;
  +    length = 0;
  +    List<Assist> assists = await _computeAssists();
       expect(assists, isEmpty);
     }
   
  
positive.code: class AssistProcessorTest_Driver extends AssistProcessorTest {
    @override
    bool get enableNewAnalysisDriver => true;
  
    @failingTest
    @override
    test_addTypeAnnotation_local_OK_addImport_notLibraryUnit() {
      return super.test_addTypeAnnotation_local_OK_addImport_notLibraryUnit();
    }
  
    @failingTest
    @override
    test_invalidSelection() {
      return super.test_invalidSelection();
    }
  }
  
  class _DartAssistContextForValues implements DartAssistContext {
  
negative.code:     Source appSource = addSource('/app.dart', appCode);
      testSource = addSource('/test.dart', testCode);
      // resolve
      if (enableNewAnalysisDriver) {
        await resolveTestUnit(testCode);
      } else {
        context.resolveCompilationUnit2(appSource, appSource);
        testUnit = context.resolveCompilationUnit2(testSource, appSource);
        testUnitElement = testUnit.element;
        testLibraryElement = testUnitElement.library;
      }
      // prepare the assist
      offset = findOffset('v = ');
      assist = await _assertHasAssist(DartAssistKind.ADD_TYPE_ANNOTATION);
  