@Override
    public void putAll(Map<K, V> map) {
        throw MODIFICATION_ATTEMPT_ERROR;
    }
@Test
    void testPutAll() throws Exception {
        assertThat(mapState.contains(1L)).isTrue();
        long value = mapState.get(1L);
        assertThat(value).isEqualTo(5L);

        assertThat(mapState.contains(2L)).isTrue();
        value = mapState.get(2L);
        assertThat(value).isEqualTo(5L);

        Map<Long, Long> nMap = new HashMap<>();
        nMap.put(1L, 7L);
        nMap.put(2L, 7L);
        assertThatThrownBy(() -> mapState.putAll(nMap))
                .isInstanceOf(UnsupportedOperationException.class);
    }