boolean isMapped(String userId) {
        return idToDirectoryNameMap.containsKey(getIdStrategy().keyFor(userId));
    }
@Test
    public void testIsMapped() throws IOException {
        UserIdMapper mapper = createUserIdMapper(IdStrategy.CASE_INSENSITIVE);
        String user1 = "user1";
        File directory = mapper.putIfAbsent(user1, true);
        assertThat(mapper.isMapped(user1), is(true));
    }