Unit testing 使用spock mocking或grails mockFor进行单元测试：空指针异常

我正在对我老板写的一些代码进行单元测试。他是个新手，我是TDD的新手，所以请和我一起集思广益

我要测试的文件，EmailAssist是此处未显示的服务的助手类。EmailAssist应参考其他几种服务，包括sectionService，如图所示。

   class EmailAssist {
       def sectionService
       //condensed to relevant items
       List<CommonsMultipartFile> attachments
       Map emailMap =[:]
       User user
       Boolean valid

       public EmailAssist(){
          valid = false
       }

       public EmailAssist(GrailsParameterMap params, User user){
              //irrelevant code here involving snipped items
              this.setSections(params.list('sections'))
              //series of other similar calls which are also delivering an NPE
       }
       //third constructor using third parameter, called in example but functionally 
       //similar to above constructor.

       //definition of errant function
       void setSections(List sections) {
            emailMap.sections = sectionService.getEmailsInSectionList(sections, user)
        }

准确的净现值如下所示： java.lang.NullPointerException:无法对null对象调用方法getEmailsInSectionList（） 在

这是我的setSections函数的主体，对于那些在家里玩游戏的人来说。NPE堆栈起源于我的测试文件中的构造函数调用。我也尝试过使用spock风格的模拟，但该服务仍然被认为是空的。最糟糕的是，构造函数甚至不是这个测试应该测试的东西，它只是拒绝通过这个测试，结果使测试无法运行

如果有任何更多的细节，我可以提供澄清的事情，让我知道，谢谢

---

编辑：我短路了构造函数中的setter来完成测试，但这在测试覆盖率中留下了一些明显的漏洞，我无法找出如何修复。也许我的嘲弄放错地方了？斯波克的模拟文档对于复杂的函数来说不是很方便。

你得到了NPE，因为

EmailAssist

中的

sectionService

没有被创建。

EmailAssist

的构造函数调用

sectionService.getEmailsInSectionList（sections，user）

并且因为

sectionService

为空，所以您得到一个NPE

尽管您在test

setup（）

中创建了一个名为

sectionService

的模拟，但它不会自动连接/注入到

EmailAssist

类中。在Grails单元测试中，自动连接非常有限——文档中没有非常清楚地说明实际创建了哪些bean（而且我对Grails/Groovy比较陌生）

您需要在创建

emailAssist

时插入

部分服务

，否则就太晚了，无法退出NPE

如果在单元测试中将对构造函数的调用修改为：

@TestMixin(GrailsUnitTestMixin)
class EmailAssistSpec extends Specification {
   @Shared
   GrailsParameterMap params
   @Shared
   GrailsMockHttpServletRequest request = new GrailsMockHttpServletRequest()
   @Shared
   User user
   @Shared
   def mockSectionService = Mock(SectionService)

   def setup() {
       user = new User(id: 1, firstName: "1", lastName: "1", username: "1", email: "1@1.com")
   }

   def cleanup(){
   }

   void testGetFiles(){
        given: "an EmailAssist class with an overridden constructor"

        EmailAssist.metaClass.constructor = { ParamsType params, RequestType request, UserType user -> 
           def instance = new EmailAssist(sectionService: mockSectionService) 
           instance // this returns instance as it's the last line in the closure, but you can put "return instance" if you wish
        }            

        // note that I've moved the population of the request to the given section
        //bunch of code to populate request
        params = newGrailsParameterMap([:], request)

        // this is the list of parameters that you expect sectionService will be called with
        def expectedSectionList = ['some', 'list']

        when: "we call the constructor"
        EmailAssist assist = new EmailAssist(params, request, user)

        then: "sectionService is called by the constructor with the expected parameters"
        1 * mockSectionService.getEmailsInSectionList(expectedSectionList, user)
        // replace a parameter with _ if you don't care about testing the parameter

---

这个答案是根据伯特·贝克维思（Burt Beckwith）的博客文章得出的。

我将要检查一下。我只是想说我已经发现了问题所在，我会看看我是否能让它工作，并告诉你我想到了什么。没有NPE，但似乎mockSectionService从未被调用过。即使我把它降格为“1*_”，它也会抱怨调用太少。不知道该怎么想。仅仅在一周后再详细说明一下：这个解决方案在某种程度上起了作用。目前还不清楚有多少构造函数被覆盖，坦率地说，由于元类工作方式的挑剔，我们放弃了该实现。具体地说，对值进行元分类本身是不一致的。例子

@TestMixin(GrailsUnitTestMixin)
class EmailAssistSpec extends Specification {
   @Shared
   GrailsParameterMap params
   @Shared
   GrailsMockHttpServletRequest request = new GrailsMockHttpServletRequest()
   @Shared
   User user
   @Shared
   def sectionService

   def setup() {
       user = new User(id: 1, firstName: "1", lastName: "1", username: "1", email: "1@1.com")
       def sectionServiceMock = mockFor(SectionService)
       sectionServiceMock.demand.getEmailsInSectionList() {
            []
       }
       sectionService = sectionServiceMock.createMock()
   }

   def cleanup(){
   }
   void testGetFiles(){
        when:
        //bunch of code to populate request

        params = newGrailsParameterMap([:], request)
        EmailAssist assist = new EmailAssist(params, request, user)
        //Above constructor call generates NPE

        emailMap.sections = sectionService.getEmailsInSectionList(sections, user)

@TestMixin(GrailsUnitTestMixin)
class EmailAssistSpec extends Specification {
   @Shared
   GrailsParameterMap params
   @Shared
   GrailsMockHttpServletRequest request = new GrailsMockHttpServletRequest()
   @Shared
   User user
   @Shared
   def mockSectionService = Mock(SectionService)

   def setup() {
       user = new User(id: 1, firstName: "1", lastName: "1", username: "1", email: "1@1.com")
   }

   def cleanup(){
   }

   void testGetFiles(){
        given: "an EmailAssist class with an overridden constructor"

        EmailAssist.metaClass.constructor = { ParamsType params, RequestType request, UserType user -> 
           def instance = new EmailAssist(sectionService: mockSectionService) 
           instance // this returns instance as it's the last line in the closure, but you can put "return instance" if you wish
        }            

        // note that I've moved the population of the request to the given section
        //bunch of code to populate request
        params = newGrailsParameterMap([:], request)

        // this is the list of parameters that you expect sectionService will be called with
        def expectedSectionList = ['some', 'list']

        when: "we call the constructor"
        EmailAssist assist = new EmailAssist(params, request, user)

        then: "sectionService is called by the constructor with the expected parameters"
        1 * mockSectionService.getEmailsInSectionList(expectedSectionList, user)
        // replace a parameter with _ if you don't care about testing the parameter