}

    @Test
    public void test_toJson_emptyMap() {
        final String json = coordinatorHelper.toJson(Map.of());
        assertEquals("{}", json);
    }

    @Test
    public void test_toJson_nestedMap() {
        final Map<String, Object> map = Map.of("query", Map.of("term", Map.of("type", "heartbeat")));
        final String json = coordinatorHelper.toJson(map);
        assertNotNull(json);