private AccessTokenHelper accessTokenHelper;

    @Override
    public void setUp() throws Exception {
        super.setUp();
        accessTokenHelper = new AccessTokenHelper();
    }

    public void test_generateAccessToken() {
        List<String> tokens = new ArrayList<String>();
        for (int i = 0; i < NUM; i++) {
            tokens.add(accessTokenHelper.generateAccessToken());
        }
        for (int i = 0; i < NUM; i++) {