anchor.diff:    }
   }
   
  -Futire expectThrowsAsync(Future future, String message) {
  +Future expectThrowsAsync(Future future, String message) {
     return future.then((r) => Expect.fail(message))
                  .catchError((e) {});
   }
  
positive.code:   }
  }
  
  void withTempDirSync(String prefix, void test(Directory dir)) async {
    var tempDir = Directory.systemTemp.createTempSync(prefix);
    try {
      test(tempDir);
  
negative.code:   Expect.equals(f.lengthSync(), 10);
  }
  
  void writeSync(Directory dir) {
    var f = new File('x');
    var raf = f.openSync(mode: WRITE_ONLY);
    raf.writeStringSync('Hello');
  