anchor.diff:  import 'package:kernel/binary/ast_to_binary.dart';
   import 'package:kernel/ast.dart' show Component;
   import 'package:mockito/mockito.dart';
  +import 'package:path/path.dart' as path;
   import 'package:test/test.dart';
   import 'package:vm/incremental_compiler.dart';
   
  
positive.code:     Directory tempDir;
      setUp(() {
        var systemTempDir = Directory.systemTemp;
        tempDir = systemTempDir.createTempSync('foo');
      });
  
      tearDown(() {
  
negative.code: 
        expect(depFile.existsSync(), true);
        var depContents = depFile.readAsStringSync();
        var depContentsParsed = depContents.split(': ');
        expect(path.basename(depContentsParsed[0]), path.basename(dillFile.path));
        expect(depContentsParsed[1], isNotEmpty);
      });
    });
  