@Override
    public void clear() {
        throw MODIFICATION_ATTEMPT_ERROR;
    }
@Test
    void testClear() throws Exception {
        String value = aggrState.get();
        assertThat(value).isEqualTo("42");
        assertThatThrownBy(() -> aggrState.clear())
                .isInstanceOf(UnsupportedOperationException.class);
    }