code: public void testQueryByProcessDefinitionKeys(){
    final Set<String> processDefinitionKeySet=new HashSet<String>(2);
    processDefinitionKeySet.add(PROCESS_DEFINITION_KEY);
    processDefinitionKeySet.add(PROCESS_DEFINITION_KEY_2);
    ProcessInstanceQuery query=runtimeService.createProcessInstanceQuery().processDefinitionKeys(processDefinitionKeySet);
    assertEquals(PROCESS_DEPLOY_COUNT,query.count());
    assertEquals(PROCESS_DEPLOY_COUNT,query.list().size());
    try {
      query.singleResult();
      fail();
    }
   catch (  ActivitiException e) {
    }
  }
  