anchor.diff:    "vm": "dartk",
   };
   
  +const configurations = {
  +  "analyzer": "analyzer-asserts-strong-linux",
  +  "cfe": "cfe-strong-linux",
  +  "dart2js": "dart2js-weak-linux-x64-d8",
  +  "ddc": "dartdevk-strong-linux-release-chrome",
  +  "vm": "dartk-strong-linux-release-x64",
  +};
  +
   void main(List<String> arguments) async {
     var testDir = "";
     var isLegacy = false;
  -  var compilers = <String>[];
  +  var compiler = "ddc";
   
     var argParser = ArgParser();
     argParser.addFlag("legacy",
  
positive.code:       negatable: false,
        callback: (flag) => isLegacy = flag);
  
    argParser.addMultiOption("compiler",
        abbr: "c",
        help: "Which Dart implementations to run the tests on.",
        allowed: ["analyzer", "cfe", "dart2js", "ddc", "vm"],
        callback: (implementations) {
      compilers.addAll(implementations.map((name) => compilerNames[name]));
    });
  
    if (arguments.contains("--help")) {
      showUsage(argParser);
  
negative.code: 
    if (!isLegacy) testDir = toNnbdPath(testDir);
  
    // DDC doesn't have a Mac bot so when running DDC tests on a Mac, use a manual
    // configuration. Otherwise, use the right named configuration.
    List<String> testArgs;
    if (Platform.isLinux || compiler != "ddc") {
      var configuration = configurations[compiler];
      if (!Platform.isLinux) {
        // TODO(rnystrom): We'll probably never need to run this script on
        // Windows, but if we do... do that.
        configuration = configuration.replaceAll("linux", "mac");
      }
  
      testArgs = ["-n$configuration", testDir];
    } else {
      testArgs = [
        "--mode=release",
        if (!isLegacy) ...[
          "--enable-experiment=non-nullable",
          "--nnbd=strong",
        ],
        "--compiler=${compilerNames[compiler]}",
        testDir,
      ];
    }
  
    print("Running tools/test.py ${testArgs.join(' ')}");
    await runProcessAsync("tools/test.py", testArgs);
  