@Override
    public String buildContext() {
        final String selector = ((Collection<?>) getSource())
                .stream()
                .map(s -> ((DashboardUserDO) s).getUserName())
                .collect(Collectors.joining(","));
        return String.format("the user[%s] is %s", selector, StringUtils.lowerCase(getType().getType().toString()));
    }
@Test
    public void batchUserDeletedContextTest() {
        BatchUserDeletedEvent batchUserDeletedEvent = new BatchUserDeletedEvent(Arrays.asList(one, two), "test-operator");

        String context = String.format("the user[%s] is %s",
                one.getUserName() + "," + two.getUserName(), StringUtils.lowerCase(EventTypeEnum.USER_DELETE.getType().toString()));

        assertEquals(context, batchUserDeletedEvent.buildContext());
    }