anchor.diff:  
   import 'package:file/file.dart';
   import 'package:file/memory.dart';
  +import 'package:flutter_tools/src/cache.dart';
   import 'package:flutter_tools/src/base/context.dart';
   import 'package:flutter_tools/src/base/io.dart';
   import 'package:flutter_tools/src/base/platform.dart';
  
positive.code:         error = 'test failed unexpectedly: $thrownError';
        });
        time.elapse(const Duration(milliseconds: 500));
        expect(processMock.lastPubCache, endsWith('flutter/.pub-cache'));
        expect(error, isNull);
      });
    }, overrides: <Type, Generator>{
  
negative.code:         error = 'test failed unexpectedly: $thrownError';
        });
        time.elapse(const Duration(milliseconds: 500));
        expect(processMock.lastPubCache, equals('custom/pub-cache/path'));
        expect(error, isNull);
      });
    }, overrides: <Type, Generator>{
      ProcessManager: () => new MockProcessManager(69),
      FileSystem: () => new MockFileSystem(),
      Platform: () => new FakePlatform(
        environment: <String, String>{'PUB_CACHE': 'custom/pub-cache/path'},
      ),
    });
  }
  