anchor.diff:  
   import 'package:analyzer/src/generated/sdk_io.dart';
   import 'package:analyzer_cli/src/driver.dart' show Driver, errorSink, outSink;
  +import 'package:analyzer_cli/src/options.dart';
   import 'package:path/path.dart' as path;
   import 'package:unittest/unittest.dart';
   
  
positive.code:   group('Sdk extensions', () {
      StringSink savedOutSink, savedErrorSink;
      int savedExitCode;
  
      setUp(() {
        savedOutSink = outSink;
        savedErrorSink = errorSink;
        savedExitCode = exitCode;
        outSink = new StringBuffer();
        errorSink = new StringBuffer();
      });
  
negative.code:       outSink = savedOutSink;
        errorSink = savedErrorSink;
        exitCode = savedExitCode;
        exitHandler = savedExitHandler;
      });
  
      test('.packages file present', () async {
        String testDir = path.join(testDirectory, 'data', 'packages_file');
        Driver driver = new Driver()
          ..start([
            '--packages',
            path.join(testDir, '.packages'),
            path.join(testDir, 'sdk_ext_user.dart')
          ]);
  
        DirectoryBasedDartSdk sdk = driver.sdk;
        expect(sdk.useSummary, isFalse);
  