Karate Netty Mock服务Schema匹配规则不生效问题及解决方案

问题背景 #

当前使用Karate 1.1.0版本构建支持可选请求对象的Mock服务：请求载荷中beneficiary节点下可二选一传入cardInfo对象（含number字段）或cardTokenInfo对象（含token字段），两种合法请求结构示例如下：

"beneficiary":{
    "cardInfo":{
        "number": "12345" 
    }
}

"beneficiary":{
    "cardTokenInfo":{
        "token": "98765"
    }
}

初始实现代码如下：

Feature: Karate netty - testing for optional. The request payload may have either benefiaciary.cardInfo object or beneficiary.cardTokenInfo object

Background:
 * def happyPathResponse_json = {status: 'Payment accepted'}
 * def invalidResponse_json = {status: 'Invalid request'}

## Happy path if cardNumber is passed
Scenario: pathMatches('/mock/payment/v5')
         && request.beneficiary.cardInfo.number == '12345'

* def response = happyPathResponse_json
* def responseStatus = 201
* def responseHeaders = {'Content-Type': 'application/json'}


## Happy path if card token is passed 
Scenario: pathMatches('/mock/payment/v5')
         && request.beneficiary.cardTokenInfo.number == '98765'

* def response = happyPathResponse_json 
* def responseStatsus = 201
* def responseHeaders = {'Content-Type':'application/json'}


## Catch all scenario if nothing matches
Scenario: pathMatches('/mock/payment/v5')
* def response = invalidRespose_json
* def responseStatus = 201
* def responseHeaders = {'Content-Type': 'application/json'}   

问题现象 #

传入携带beneficiary.cardInfo的请求时逻辑可正常运行，但传入携带beneficiary.cardTokenInfo的请求时，Karate Netty服务抛出错误：

Cannot read property "number" from undefined

原因分析 #

该报错符合预期：第一个场景的匹配逻辑会直接读取不存在的cardInfo节点下的number属性，导致流程中断无法进入后续场景。
最初尝试在场景匹配条件中加入Schema校验逻辑，判断当beneficiary.cardInfo == '#present'时才匹配对应场景，代码如下：

Scenario: pathMatches('/mock/payment/v5')
             && request.beneficiary.cardInfo == '#present' 
             && request.beneficiary.cardInfo.number == '12345'
   * def response = happyPathResponse_json
   * def responseStatus = 201
   * def responseHeaders = {'Content-Type': 'application/json'}

但该Schema匹配写法仅在普通Karate测试用例中可正常生效，在Netty Mock服务中始终返回false无法匹配。
* if() karate.abort()方案不适用，该写法会终止当前Feature执行，导致后续场景无法运行。
后续排查中尝试使用bodyPath方法实现路径安全读取，将request.beneficiary.cardInfo.number == '12345'替换为bodyPath('$.beneficiary.cardInfo.number') == '12345'后可解决路径不存在的报错问题，但'#present'标记仍无法正常使用。

可行解决方案 #

Mock场景匹配条件仅支持原生JS逻辑，共有两种可落地的修复方案：

• 方案1：使用bodyPath方法做安全路径取值匹配，直接读取JSON路径值做判断，不存在的路径会返回null不会抛出异常

  Scenario: pathMatches('/mock/payment/v5')
           && bodyPath('$.beneficiary.cardInfo.number') == '12345'
  * def response = happyPathResponse_json
  * def responseStatus = 201
  * def responseHeaders = {'Content-Type': 'application/json'}
  

• 方案2：通过karate.match方法先判断字段是否存在，再做值匹配

  Scenario: pathMatches('/mock/payment/v5')
           && karate.match("request.beneficiary.cardInfo == '#present'").pass 
           && request.beneficiary.cardInfo.number == '12345'
  * def response = happyPathResponse_json
  * def responseStatus = 201
  * def responseHeaders = {'Content-Type': 'application/json'}
  

避坑提示 #

网传直接使用request.beneficiary.cardInfo.number.contains('12345')的写法存在缺陷，当请求传入cardInfo下的未知字段时会直接触发报错，异常请求示例如下：

"beneficiary":{
    "cardInfo":{
        "someUnknownKey": "12345" 
    }
}

内容的提问来源于stack exchange，提问作者Dinesh Arora