@Override
    public void accumulate(Object value) {
        if (value != null && !values.add(value)) {
            return;
        }

        delegate.accumulate(value);
    }
@Test
    public void test_accumulate() {
        SqlAggregation aggregation = new DistinctSqlAggregation(delegate);
        aggregation.accumulate("1");
        aggregation.accumulate("2");
        aggregation.accumulate("1");

        verify(delegate).accumulate("1");
        verify(delegate).accumulate("2");
        verifyNoMoreInteractions(delegate);
    }