anchor.diff:  
       final libFile = provider.newFile(
           _p('/workspace/.dart_tool/build/generated/foo/lib/file.dart'), '');
  -    expect(workspace.builtFile('lib/file.dart', 'foo'), libFile);
  +    expect(workspace.builtFile(_p('lib/file.dart'), 'foo'), libFile);
     }
   
     void test_builtFile_notInPackagesGetsHidden() {
  
positive.code: 
      final webFile = provider.newFile(
          _p('/workspace/.dart_tool/build/generated/project/web/file.dart'), '');
      expect(workspace.findFile('/workspace/web/file.dart'), webFile);
    }
  
    PackageBuildWorkspace _createWorkspace(
  
negative.code: 
    Uri addPackageSource(String path, String uriStr, {bool create: true}) {
      Uri uri = Uri.parse(uriStr);
      final File file = create
          ? provider.newFile(_p(path), '')
          : provider.getResource(_p(path));
      final Source source = file.createSource(uri);
      when(packageUriResolver.resolveAbsolute(uri)).thenReturn(source);
      return uri;
  