anchor.diff:                        file.deleteHandler = () {
                           file.existsHandler = (exists) {
                             Expect.isFalse(exists);
  -                          asyncTestDone();
  +                          asyncTestDone("testAppend");
                           };
                           file.exists();
                         };
  
positive.code:         testAppendSync();
          testWriteAppend();
          testOutputStreamWriteAppend();
          asyncTestDone();
        });
    }
  }
  
negative.code:     file.createSync();
      List<int> buffer = content.charCodes();
      OutputStream outStream = file.openOutputStream();
      outStream.write(buffer);
      outStream.close();
      File file2 = new File(filename);
      OutputStream appendingOutput = file2.openOutputStream(FileMode.APPEND);
      appendingOutput.write(buffer);
      appendingOutput.close();
      File file3 = new File(filename);
      file3.openHandler = (RandomAccessFile openedFile) {
        openedFile.lengthHandler = (int length) {
          Expect.equals(content.length * 2, length);
          openedFile.closeHandler = () {
            file3.deleteHandler = () {
              asyncTestDone("testOutputStreamWriteAppend");
            };
            file3.delete();
          };
          openedFile.close();
        };
        openedFile.length();
      };
      file3.open();
      asyncTestStarted();
    }
  
  
    static void testReadWriteSync() {
      // Read a file.
      String inFilename = getFilename("tests/vm/data/fixed_length_file");
  