Spock/Groovy测试同时验证调用次数与异常失败，单独验证正常？

问题场景 #

在Spock/Groovy测试中，当同一个测试用例同时验证方法调用次数和抛出的异常时，测试失败；但单独验证任意一项时，测试均可正常通过。

可正常通过的测试用例1（仅验证异常） #

def "should throw AppointmentNotFoundException when appointment do not exist" () {
  given:
  long nonExistingAppointmentId = 69L

  when:
  appointmentRepository.findById(nonExistingAppointmentId) >> { throw new AppointmentNotFoundException("Appointment with id " + nonExistingAppointmentId + " not found") }
  findAppointmentQueryHandler.handle(nonExistingAppointmentId)

  then:
  thrown(AppointmentNotFoundException)
}

可正常通过的测试用例2（仅验证方法调用次数） #

def "should throw AppointmentNotFoundException when appointment do not exist" () {
  given:
  long nonExistingAppointmentId = 69L

  when:
  appointmentRepository.findById(nonExistingAppointmentId) >> { throw new AppointmentNotFoundException("Appointment with id " + nonExistingAppointmentId + " not found") }
  findAppointmentQueryHandler.handle(nonExistingAppointmentId)

  then:
  1 * appointmentRepository.findById(69L)
}

合并后失败的测试用例 #

def "should throw AppointmentNotFoundException when appointment do not exist" () {
  given:
  long nonExistingAppointmentId = 69L

  when:
  appointmentRepository.findById(nonExistingAppointmentId) >> { throw new AppointmentNotFoundException("Appointment with id " + nonExistingAppointmentId + " not found") }
  findAppointmentQueryHandler.handle(nonExistingAppointmentId)

  then:
  1 * appointmentRepository.findById(69L)
  thrown(AppointmentNotFoundException)
}

错误信息 #

Expected exception of type 'com.bbc.anotherhospital.exceptions.AppointmentNotFoundException', but no exception was thrown
    at org.spockframework.lang.SpecInternals.checkExceptionThrown(SpecInternals.java:84)
    at org.spockframework.lang.SpecInternals.thrownImpl(SpecInternals.java:71)
    at com.bbc.anotherhospital.appointment.handlers.FindAppointmentQueryHandlerSpec.should throw AppointmentNotFoundException when appointment do not exist

依赖配置 #

<dependency>
  <groupId>org.apache.groovy</groupId>
  <artifactId>groovy-all</artifactId>
  <version>4.0.15</version>
  <type>pom</type>
</dependency>
<dependency>
  <groupId>org.spockframework</groupId>
  <artifactId>spock-core</artifactId>
  <version>2.4-M1-groovy-4.0</version>
  <scope>test</scope>
</dependency>

问题原因及解决方案 #

原因 #

Spock中，交互断言（如1 * 方法调用）的优先级高于存根（>>）设置。当你在then块中添加1 * appointmentRepository.findById(69L)时，该断言会覆盖你之前在when块中设置的存根行为（抛出异常），此时findById方法会返回对应类型的默认值（如null），而非抛出异常，导致thrown断言失败。

解决方案 #

有两种可行的修正方式：

方式1：将存根行为与交互断言合并

把存根的抛出异常逻辑直接整合到交互断言中，确保调用次数和行为同时生效：

def "should throw AppointmentNotFoundException when appointment do not exist" () {
  given:
  long nonExistingAppointmentId = 69L

  when:
  findAppointmentQueryHandler.handle(nonExistingAppointmentId)

  then:
  1 * appointmentRepository.findById(nonExistingAppointmentId) >> { 
    throw new AppointmentNotFoundException("Appointment with id " + nonExistingAppointmentId + " not found") 
  }
  thrown(AppointmentNotFoundException)
}

方式2：将存根设置移至given块

将存根逻辑放在测试准备阶段的given块中，then块仅验证调用次数和异常：

def "should throw AppointmentNotFoundException when appointment do not exist" () {
  given:
  long nonExistingAppointmentId = 69L
  appointmentRepository.findById(nonExistingAppointmentId) >> { 
    throw new AppointmentNotFoundException("Appointment with id " + nonExistingAppointmentId + " not found") 
  }

  when:
  findAppointmentQueryHandler.handle(nonExistingAppointmentId)

  then:
  1 * appointmentRepository.findById(nonExistingAppointmentId)
  thrown(AppointmentNotFoundException)
}

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