Mockito doThrow() 方法使我的测试因给定异常而失败

Question

我正在测试注入的StatefulBeanToCsv依赖项引发异常的错误情况。 但是，Mockito 的doThrow()方法只是让我的测试失败，而不是允许使用assertThrows()验证该异常。

我通过BeanFactory而不是构造函数/设置器注入注入我的StatefulBeanToCsv依赖项，因为我需要将Writer作为参数传递给它。

测试如下，星号处失败。 CSV bean 在我的成功测试中工作正常 - 在这种情况下我能想到的主要区别是使用do / when Mockito 模式而不是when / then在其他地方使用的模式（它不允许从无效方法）：

@Test
    void willThrowSwaggerListToCsvExceptionIfCsvWriterThrowsCsvException() throws CsvFieldAssignmentException {
        // given
        List<ApiSummary.Endpoint> endpointList = getEndpointList(6);
        doReturn(endpointBeanToCsvMock)
                .when(beanFactoryMock).getBean(eq(StatefulBeanToCsv.class), eq(ApiSummary.Endpoint.class), any(Writer.class), any(String[].class));
        doThrow(CsvFieldAssignmentException.class)
*               .when(endpointBeanToCsvMock).write(endpointList);
        // when, then
        assertThrows(SwaggerToCsvException.class, () -> underTest.listToResource(endpointList, ApiSummary.Endpoint.class));
    }

我正在测试的方法如下（我希望星号处的 void “write” 方法抛出异常）。

public <T> ByteArrayResource listToResource(List<T> beanList, Class<T> clazz, String... columnOrder) {
        ByteArrayOutputStream out = new ByteArrayOutputStream();
        try (Writer writer = new OutputStreamWriter(out)) {
            StatefulBeanToCsv<T> beanToCsv = beanFactory.getBean(StatefulBeanToCsv.class, clazz, writer, columnOrder);
*           beanToCsv.write(beanList);
        } catch (CsvFieldAssignmentException | IOException e) {
            throw new SwaggerToCsvException("Error converting List of type " + clazz.getSimpleName() + " to csv", e);
        }
        byte[] bytes = out.toByteArray();
        return new ByteArrayResource(bytes);
    }

我错过了什么吗？

编辑 - 堆栈跟踪：

java.lang.InstantiationError: com.opencsv.exceptions.CsvFieldAssignmentException

    at jdk.internal.reflect.GeneratedSerializationConstructorAccessor3.newInstance(Unknown Source)
    at java.base/java.lang.reflect.Constructor.newInstance(Constructor.java:490)
    at org.objenesis.instantiator.sun.SunReflectionFactoryInstantiator.newInstance(SunReflectionFactoryInstantiator.java:48)
    at org.objenesis.ObjenesisBase.newInstance(ObjenesisBase.java:73)
    at org.mockito.internal.creation.instance.ObjenesisInstantiator.newInstance(ObjenesisInstantiator.java:21)
    at org.mockito.internal.stubbing.answers.ThrowsExceptionForClassType.getThrowable(ThrowsExceptionForClassType.java:23)
    at org.mockito.internal.stubbing.answers.AbstractThrowsException.validateFor(AbstractThrowsException.java:43)
    at org.mockito.internal.stubbing.InvocationContainerImpl.addAnswer(InvocationContainerImpl.java:72)
    at org.mockito.internal.stubbing.InvocationContainerImpl.setMethodForStubbing(InvocationContainerImpl.java:128)
    at org.mockito.internal.handler.MockHandlerImpl.handle(MockHandlerImpl.java:53)
    at org.mockito.internal.handler.NullResultGuardian.handle(NullResultGuardian.java:29)
    at org.mockito.internal.handler.InvocationNotifierHandler.handle(InvocationNotifierHandler.java:33)
    at org.mockito.internal.creation.bytebuddy.MockMethodInterceptor.doIntercept(MockMethodInterceptor.java:82)
    at org.mockito.internal.creation.bytebuddy.MockMethodInterceptor.doIntercept(MockMethodInterceptor.java:56)
    at org.mockito.internal.creation.bytebuddy.MockMethodInterceptor$DispatcherDefaultingToRealMethod.interceptSuperCallable(MockMethodInterceptor.java:141)
    at com.opencsv.bean.StatefulBeanToCsv$MockitoMock$321003460.write(Unknown Source)
    at com.foo.myproject.csv.CsvFactoryTest.willThrowSwaggerListToCsvExceptionIfCsvWriterThrowsCsvException(CsvFactoryTest.java:96)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.base/java.lang.reflect.Method.invoke(Method.java:566)
    at org.junit.platform.commons.util.ReflectionUtils.invokeMethod(ReflectionUtils.java:688)
    at org.junit.jupiter.engine.execution.MethodInvocation.proceed(MethodInvocation.java:60)
    at org.junit.jupiter.engine.execution.InvocationInterceptorChain$ValidatingInvocation.proceed(InvocationInterceptorChain.java:131)
    at org.junit.jupiter.engine.extension.TimeoutExtension.intercept(TimeoutExtension.java:149)
    at org.junit.jupiter.engine.extension.TimeoutExtension.interceptTestableMethod(TimeoutExtension.java:140)
    at org.junit.jupiter.engine.extension.TimeoutExtension.interceptTestMethod(TimeoutExtension.java:84)
    at org.junit.jupiter.engine.execution.ExecutableInvoker$ReflectiveInterceptorCall.lambda$ofVoidMethod$0(ExecutableInvoker.java:115)
    at org.junit.jupiter.engine.execution.ExecutableInvoker.lambda$invoke$0(ExecutableInvoker.java:105)
    at org.junit.jupiter.engine.execution.InvocationInterceptorChain$InterceptedInvocation.proceed(InvocationInterceptorChain.java:106)
    at org.junit.jupiter.engine.execution.InvocationInterceptorChain.proceed(InvocationInterceptorChain.java:64)
    at org.junit.jupiter.engine.execution.InvocationInterceptorChain.chainAndInvoke(InvocationInterceptorChain.java:45)
    at org.junit.jupiter.engine.execution.InvocationInterceptorChain.invoke(InvocationInterceptorChain.java:37)
    at org.junit.jupiter.engine.execution.ExecutableInvoker.invoke(ExecutableInvoker.java:104)
    at org.junit.jupiter.engine.execution.ExecutableInvoker.invoke(ExecutableInvoker.java:98)
    at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.lambda$invokeTestMethod$6(TestMethodTestDescriptor.java:210)
    at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
    at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.invokeTestMethod(TestMethodTestDescriptor.java:206)
    at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.execute(TestMethodTestDescriptor.java:131)
    at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.execute(TestMethodTestDescriptor.java:65)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$5(NodeTestTask.java:139)
    at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$7(NodeTestTask.java:129)
    at org.junit.platform.engine.support.hierarchical.Node.around(Node.java:137)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$8(NodeTestTask.java:127)
    at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.executeRecursively(NodeTestTask.java:126)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.execute(NodeTestTask.java:84)
    at java.base/java.util.ArrayList.forEach(ArrayList.java:1541)
    at org.junit.platform.engine.support.hierarchical.SameThreadHierarchicalTestExecutorService.invokeAll(SameThreadHierarchicalTestExecutorService.java:38)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$5(NodeTestTask.java:143)
    at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$7(NodeTestTask.java:129)
    at org.junit.platform.engine.support.hierarchical.Node.around(Node.java:137)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$8(NodeTestTask.java:127)
    at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.executeRecursively(NodeTestTask.java:126)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.execute(NodeTestTask.java:84)
    at java.base/java.util.ArrayList.forEach(ArrayList.java:1541)
    at org.junit.platform.engine.support.hierarchical.SameThreadHierarchicalTestExecutorService.invokeAll(SameThreadHierarchicalTestExecutorService.java:38)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$5(NodeTestTask.java:143)
    at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$7(NodeTestTask.java:129)
    at org.junit.platform.engine.support.hierarchical.Node.around(Node.java:137)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$8(NodeTestTask.java:127)
    at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.executeRecursively(NodeTestTask.java:126)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.execute(NodeTestTask.java:84)
    at org.junit.platform.engine.support.hierarchical.SameThreadHierarchicalTestExecutorService.submit(SameThreadHierarchicalTestExecutorService.java:32)
    at org.junit.platform.engine.support.hierarchical.HierarchicalTestExecutor.execute(HierarchicalTestExecutor.java:57)
    at org.junit.platform.engine.support.hierarchical.HierarchicalTestEngine.execute(HierarchicalTestEngine.java:51)
    at org.junit.platform.launcher.core.EngineExecutionOrchestrator.execute(EngineExecutionOrchestrator.java:108)
    at org.junit.platform.launcher.core.EngineExecutionOrchestrator.execute(EngineExecutionOrchestrator.java:88)
    at org.junit.platform.launcher.core.EngineExecutionOrchestrator.lambda$execute$0(EngineExecutionOrchestrator.java:54)
    at org.junit.platform.launcher.core.EngineExecutionOrchestrator.withInterceptedStreams(EngineExecutionOrchestrator.java:67)
    at org.junit.platform.launcher.core.EngineExecutionOrchestrator.execute(EngineExecutionOrchestrator.java:52)
    at org.junit.platform.launcher.core.DefaultLauncher.execute(DefaultLauncher.java:96)
    at org.junit.platform.launcher.core.DefaultLauncher.execute(DefaultLauncher.java:75)
    at com.intellij.junit5.JUnit5IdeaTestRunner.startRunnerWithArgs(JUnit5IdeaTestRunner.java:71)
    at com.intellij.rt.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:33)
    at com.intellij.rt.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:220)
    at com.intellij.rt.junit.JUnitStarter.main(JUnitStarter.java:53)

Answer 1

正如 M.Deinum 在评论中提到的那样，这里的错误不是抛出异常，而是 Mockito 未能实例化异常，以便为您抛出异常。

请注意， Mockito 文档中的示例显示了正在实例化的异常 - 也就是说， doThrow()方法正在获取异常的实例，而不是您要抛出的异常的 class：

doThrow(new RuntimeException()).when(mockedList).clear();

Javadoc也确实表明您可以提供 class，就像您一样，并说它将被实例化，但没有详细说明需要哪些构造函数。 如果不亲自尝试，我猜这仅适用于具有默认（无参数）构造函数的异常。