anchor.diff:          values: System.names,
           defaultsTo: Platform.operatingSystem,
           hide: true),
  +    _Option('sanitizer', 'Sanitizer in which to run the tests.',
  +        defaultsTo: Sanitizer.none.name, values: ['all', ...Sanitizer.names]),
       _Option(
           'named_configuration',
           '''The named test configuration that supplies the values for all
  
positive.code: class OptionsParser {
    static final List<_Option> _options = [
      _Option('mode', 'Mode in which to run the tests.',
          abbr: 'm', values: ['all']..addAll(Mode.names)),
      _Option('sanitizer', 'Sanitizer in which to run the tests.',
          defaultsTo: Sanitizer.none.name,
          values: ['all']..addAll(Sanitizer.names)),
      _Option(
          'compiler',
          '''How the Dart code should be compiled or statically processed.
  
  none:          Do not compile the Dart code.
  precompiler:   Compile into AOT snapshot before running the test.
  dart2js:       Compile to JavaScript using dart2js.
  dart2analyzer: Perform static analysis on Dart code using the analyzer.
  compareAnalyzerCfe: Compare analyzer and common front end representations.
  app_jit:       Compile the Dart code into an app snapshot.
  app_jitk:      Compile the Dart code into Kernel and then into an app snapshot.
  dartk:         Compile the Dart code into Kernel before running test.
  dartkb:        Compile the Dart code into Kernel with bytecode before running test.
  dartkp:        Compile the Dart code into Kernel and then Kernel into AOT
                 snapshot before running the test.
  spec_parser:   Parse Dart code using the specification parser.''',
          abbr: 'c',
          values: Compiler.names),
      _Option(
  
negative.code:     }
  
      var runtimeNames = data["runtime"] as String;
      var runtimes = [
        if (runtimeNames != null) ...runtimeNames.split(",").map(Runtime.find)
      ];
  
      var compilerNames = data["compiler"] as String;
      var compilers = [
        if (compilerNames != null) ...compilerNames.split(",").map(Compiler.find)
      ];
  
      // Pick default compilers or runtimes if only one or the other is provided.
      if (runtimes.isEmpty) {
  