public void setup() {
    mapping =
        (ManyToManyMapping)
            getSession()
                .getProject()
                .getDescriptor(AggregateEntityMapHolder.class)
                .getMappingForAttributeName("aggregateToEntityMap");
    oldFetchJoinValue = mapping.getJoinFetch();
    mapping.setJoinFetch(fetchJoinRelationship);
    getSession()
        .getProject()
        .getDescriptor(AggregateEntityMapHolder.class)
        .reInitializeJoinedAttributes();

    UnitOfWork uow = getSession().acquireUnitOfWork();
    AggregateEntityMapHolder holder = new AggregateEntityMapHolder();
    EntityMapValue value = new EntityMapValue();
    value.setId(1);
    AggregateMapKey key = new AggregateMapKey();
    key.setKey(11);
    holder.addAggregateToEntityMapItem(key, value);

    EntityMapValue value2 = new EntityMapValue();
    value2.setId(2);
    key = new AggregateMapKey();
    key.setKey(22);
    holder.addAggregateToEntityMapItem(key, value2);
    uow.registerObject(holder);
    uow.registerObject(value);
    uow.registerObject(value2);
    uow.commit();
    holderExp = (new ExpressionBuilder()).get("id").equal(holder.getId());
    getSession().getIdentityMapAccessor().initializeAllIdentityMaps();
  }