anchor.diff:  class TestRunnerJIT implements TestRunner {
     TestRunnerJIT(Map<String, String> e, String top, String mode) {
       tag = TestRunner.getTag(mode);
  -    env = Map<String, String>.from(e);
  -    env['PATH'] = "$top/out/$tag:${env['PATH']}";
  +    dart = '$top/out/$tag/dart';
  +    env = e;
     }
     String description() {
       return "JIT-${tag}";
     }
   
     TestResult run(String fileName) {
  -    return runCommand(['dart', fileName], env);
  +    return runCommand(['$dart', fileName], env);
     }
   
     String tag;
  +  String dart;
     Map<String, String> env;
   }
   
  
positive.code:   }
  
    TestResult run(String fileName) {
      TestResult result = runCommand(['precompiler2', fileName, 'snapshot'], env);
      if (result.code != ResultCode.success) {
        return result;
      }
      return runCommand(['dart_precompiled_runtime2', 'snapshot'], env);
    }
  
    String tag;
    Map<String, String> env;
  }
  
  /// Concrete test runner of Dart2JS.
  class TestRunnerJS implements TestRunner {
    TestRunnerJS(Map<String, String> e, String top, String mode) {
      env = Map<String, String>.from(e);
      env['PATH'] = "$top/out/ReleaseX64/dart-sdk/bin:${env['PATH']}";
    }
    String description() {
      return "Dart2JS";
    }
  
    TestResult run(String fileName) {
      TestResult result = runCommand(['dart2js', fileName], env);
      if (result.code != ResultCode.success) {
        return result;
      }
      return runCommand(['nodejs', 'out.js'], env);
    }
  
    Map<String, String> env;
  }
  
  
negative.code: class TestRunnerAOT implements TestRunner {
    TestRunnerAOT(Map<String, String> e, String top, String mode) {
      tag = TestRunner.getTag(mode);
      precompiler = '$top/pkg/vm/tool/precompiler2';
      dart = '$top/pkg/vm/tool/dart_precompiled_runtime2';
      env = Map<String, String>.from(e);
      env['DART_CONFIGURATION'] = tag;
    }
    String description() {
  