@Test
public void testValidationOk() {

    DataSetLookup lookup = DataSetLookupFactory.newDataSetLookupBuilder()
            .group(DATE).fixed(DateIntervalType.MONTH, true)
            .column(DATE)
            .column(AMOUNT, AggregateFunctionType.SUM)
            .buildLookup();
    ValidationError error = TWO_COLUMNS_GROUPED.check(lookup, METADATA);
    assertNull(error);
}