@Override
    public void put(K key, V value) {
        throw MODIFICATION_ATTEMPT_ERROR;
    }
@Test
    void testPut() 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);
        assertThatThrownBy(() -> mapState.put(2L, 54L))
                .isInstanceOf(UnsupportedOperationException.class);
    }