@Test
public void testInvalidJsonFile() throws IOException {

  // given
  int numNotes = notebookRepo.list(null).size();
  // when create invalid json file
  File testNoteDir = new File(mainNotebookDir, "test");
  testNoteDir.mkdir();
  FileUtils.writeStringToFile(new File(testNoteDir, "note.json"), "");
  // then
  assertEquals(numNotes, notebookRepo.list(null).size());
}