code: @Deployment public void testUpdateExistingBusinessKey(){
    runtimeService.startProcessInstanceByKey("businessKeyProcess","testKey");
    ProcessInstance processInstance=runtimeService.createProcessInstanceQuery().singleResult();
    assertEquals("testKey",processInstance.getBusinessKey());
    if (processEngineConfiguration.getHistoryLevel().isAtLeast(HistoryLevel.ACTIVITY)) {
      HistoricProcessInstance historicProcessInstance=historyService.createHistoricProcessInstanceQuery().singleResult();
      assertEquals("testKey",historicProcessInstance.getBusinessKey());
    }
    runtimeService.updateBusinessKey(processInstance.getId(),"newKey");
    processInstance=runtimeService.createProcessInstanceQuery().singleResult();
    assertEquals("newKey",processInstance.getBusinessKey());
    if (processEngineConfiguration.getHistoryLevel().isAtLeast(HistoryLevel.ACTIVITY)) {
      HistoricProcessInstance historicProcessInstance=historyService.createHistoricProcessInstanceQuery().singleResult();
      assertEquals("newKey",historicProcessInstance.getBusinessKey());
    }
  }
  