anchor.diff:  
         // simulate package
         await _createPackage(fs, 'somepkg', 'somefile.txt');
  -
  -      devFS = DevFS(vmService, 'test', tempDir);
         await devFS.create();
         vmService.expectMessages(<String>['create test']);
         expect(devFS.assetPathsToEvict, isEmpty);
  
positive.code:   String filePath;
    Directory tempDir;
    String basePath;
    DevFS devFS;
  
    setUpAll(() {
      fs = MemoryFileSystem();
  
negative.code:       // simulate package
        await _createPackage(fs, 'somepkg', 'somefile.txt');
  
        await devFS.create();
        vmService.expectMessages(<String>['create test']);
        expect(devFS.assetPathsToEvict, isEmpty);
  