anchor.diff:  
   import 'package:file/file.dart';
   import 'package:file/memory.dart';
  +import 'package:flutter_tools/src/artifacts.dart';
   import 'package:flutter_tools/src/base/platform.dart';
   import 'package:flutter_tools/src/build_info.dart';
   import 'package:flutter_tools/src/cache.dart';
  +import 'package:flutter_tools/src/compile.dart';
   import 'package:flutter_tools/src/device.dart';
   import 'package:flutter_tools/src/tester/flutter_tester.dart';
  +import 'package:mockito/mockito.dart';
   import 'package:process/process.dart';
   
   import '../src/common.dart';
  
positive.code:           await device.startApp(null,
                mainPath: mainPath,
                debuggingOptions: new DebuggingOptions.disabled(
                    const BuildInfo(BuildMode.debug, null)));
          }, throwsToolExit());
        }, overrides: startOverrides);
  
  
negative.code:               .codeUnits
          ]));
  
          when(mockKernelCompiler.compile(
            sdkRoot: anyNamed('sdkRoot'),
            incrementalCompilerByteStorePath: anyNamed('incrementalCompilerByteStorePath'),
            mainPath: anyNamed('mainPath'),
            outputFilePath: anyNamed('outputFilePath'),
            depFilePath: anyNamed('depFilePath'),
            trackWidgetCreation: anyNamed('trackWidgetCreation'),
            extraFrontEndOptions: anyNamed('extraFrontEndOptions'),
            fileSystemRoots: anyNamed('fileSystemRoots'),
            fileSystemScheme: anyNamed('fileSystemScheme'),
            packagesPath: anyNamed('packagesPath'),
          )).thenAnswer((_) async {
            fs.file('$mainPath.dill').createSync(recursive: true);
            return new CompilerOutput('$mainPath.dill', 0);
          });
  
          final LaunchResult result = await device.startApp(null,
              mainPath: mainPath,
              debuggingOptions: new DebuggingOptions.enabled(
                  const BuildInfo(BuildMode.debug, null, previewDart2: true)));
          expect(result.started, isTrue);
          expect(result.observatoryUri, observatoryUri);
  
  