How about something like this...
def mockC = mockFor(org.hibernate.Criteria)
mockC.demand.list { return []} //PagedResultList constructor calls this
def pagedList = new PagedResultList(null, mockC.createMock()){
{
//Using a static block to set private variables
//since we can't call a constructor here!
list = yourList
totalCount = yourList.size()
}
}