testSeek() {
    if (!fsExists) {
      return;
    }

    const deferredFile = loadFile('test', FsDirectoryEntry.Behavior.CREATE);
    return deferredFile.then(goog.partial(writeToFile, 'test content'))
        .then((file) => file.createWriter())
        .then(goog.partial(checkReadyState, FsFileSaver.ReadyState.INIT))
        .then((writer) => {
          writer.seek(5);
          writer.write(googFsBlob.getBlob('stuff and things'));
          return writer;
        })
        .then(goog.partial(checkReadyState, FsFileSaver.ReadyState.WRITING))
        .then(goog.partial(waitForEvent, FsFileSaver.EventType.WRITE))
        .then(() => deferredFile)
        .then(goog.partial(checkFileContent, 'test stuff and things'));
  }
@suppress {checkTypes} suppression added to enable type
                 checking