unit-testing - 使用 spock mocking 或 grails mockFor : Null pointer exception 进行单元测试

Question

我正在对老板编写的一些代码进行单元测试。他正在画空白，而我是 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辅助类。 EmailAssist 应该引用其他几个服务，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)
        }

被调用的SectionService部分如下。

       Set<String> getEmailsInSectionList(List<String> sections, User user) {
            if(sections && user){
                //code to call DB and update list
            }
            else{
            []
            }

我的测试没有提供一个部分，所以这应该返回一个空列表，特别是因为我什至无法在单元测试中访问数据库。

单元测试如下。这是使用 mockFor，因为 spock 的模拟功能似乎并不是我所需要的。

@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

具体的NPE如下:java.lang.NullPointerException:无法在空对象上调用方法 getEmailsInSectionList()在

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

这是我的 setSections 函数的主体，供那些在家玩的人使用。 NPE 堆栈源 self 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，但该服务仍被视为 null。最糟糕的是，构造函数甚至不是该测试应该测试的内容，它只是拒绝传递它，结果导致测试无法运行。

如果我可以提供更多详细信息来澄清问题，请告诉我，谢谢!

编辑:我将构造函数中的 setter 短路以完成测试，但这在测试覆盖率中留下了一些我无法弄清楚如何修复的明显漏洞。也许我的 mock 位于错误的地方？ Spock 的模拟文档对于复杂函数不是很方便。

Answer 1

您收到 NPE 是因为未创建 EmailAssist 中的 sectionService。 EmailAssist 的构造函数调用 sectionService.getEmailsInSectionList(sections, user) 并且因为 sectionService 为 null，所以您得到一个 NPE。

虽然您在测试 setup() 中创建了一个名为 sectionService 的模拟，但它不会自动连接/注入(inject)到 EmailAssist类(class)。您在 Grails 单元测试中获得的自动连接非常有限——文档并不清楚实际创建了什么 bean(而且我对 Grails/Groovy 还比较陌生)。

您需要在创建emailAssist 时注入(inject)sectionService，否则为时已​​晚，无法逃脱NPE。

如果您将单元测试中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

此答案基于 Burt Beckwith 的博文 here .