public Set<String> getRolesBy(String userName) {
        return _rolesPerUsers.getOrDefault(userName, Collections.emptySet());
    }
@Test
    public void testGetRolesPerUsers() {
        KafkaCruiseControlConfig cruiseControlConfig = setupConfigurations(true);

        UserPermissionsManager userPermissionsManager = new UserPermissionsManager(cruiseControlConfig);

        assertEquals(new HashSet<>(Arrays.asList("ADMIN", "USER")), userPermissionsManager.getRolesBy("ccTestAdmin"));
        assertEquals(new HashSet<>(Arrays.asList("USER", "VIEWER")), userPermissionsManager.getRolesBy("ccTestUser"));
        assertEquals(Collections.singleton("VIEWER"), userPermissionsManager.getRolesBy("ccTestUser2"));
        assertEquals(Collections.singleton("ADMIN"), userPermissionsManager.getRolesBy("kafka"));
    }