### Question:
SolrCriterionTransformer { public String and(String criterion) { if (StringUtils.isEmpty(criterion)) { return StringUtils.EMPTY; } return "+(" + criterion + ")"; }  String transformToEqualsCriterionWithParsing(F field, String value); String transformToEqualsCriterion(F field, String value); String transformToEqualsCriterion(F field, String value, Operator operator); String transformToEqualsCriterion(F field, Integer value); String transformToEqualsCriterion(F field, Long value); String transformToEqualsCriterion(F field, Enum<?> enumValue); String transformToEqualsCriteria(F field, List<String> values, Operator operator); String transformToEqualsEnumCriteria(F field, List<? extends Enum<?>> values, Operator operator); String transformToDateRangeCriterion(F field, LocalDate from, LocalDate to); String transformToRangeCriterion(F field, String from, String to); String and(String criterion); String join(List<String> criteria);  }### Answer:
@Test public void and() { String actual = criterionTransformer.and("aa:bb"); assertEquals("+(aa:bb)", actual); }