anchor.diff:  import 'dart:isolate' show
       ReceivePort;
   
  -import 'dart:async' show
  -    Future;
  -
  -import 'package:rasta/testing.dart' show
  +import '../testing.dart' show
       TestDescription,
       dartArguments,
       dartSdk,
       listTests,
       startDart;
   
  -main() async {
  +Uri testRoot;
  +
  +main(List<String> arguments) async {
  +  testRoot = Uri.base.resolve(arguments.single);
     final ReceivePort port = new ReceivePort();
     List<TestDescription> descriptions =
  -      await listTests(<Uri>[Platform.script.resolve(".")]).toList();
  +      await listTests(<Uri>[testRoot.resolve(".")]).toList();
     descriptions.sort();
     List<TestDescription> unitTests = <TestDescription>[];
     List<TestDescription> goldenTests = <TestDescription>[];
  
positive.code:   }
    await analyzeTests(unitTests);
    StringBuffer sb = new StringBuffer();
    sb.writeln("library testa_combined;\n");
    sb.writeln("import '${Platform.script.path}' show runTests;\n");
    for (TestDescription description in unitTests) {
      String shortName = description.shortName.replaceAll("/", "__");
      sb.writeln(
  
negative.code:         "show main;");
    }
    sb.writeln("\nvoid main() {");
    sb.writeln("  Directory.current = '${testRoot.resolve('..').toFilePath()}';");
    sb.writeln("  runTests(<String, Function> {");
    for (TestDescription description in unitTests) {
      String shortName = description.shortName.replaceAll("/", "__");
  