问题

以下是您提供的代码片段的翻译部分：

我正在研究如何使用Mockito和JUnit，并且现在正在测试一些代码片段。我不明白为什么在以下代码中使用Mock注解后会出现空指针异常（NPE）：

    @RunWith(MockitoJUnitRunner.class)
    public class MockitoTest{
	    @Test
	    public void whenNotUseMockAnnotation() {
	        List mockList = mock(ArrayList.class);
	    
	        mockList.add("one");
	        verify(mockList).add("one");
	        assertEquals(0, mockList.size());
	 
	        when(mockList.size()).thenReturn(100);
	        assertEquals(100, mockList.size());
	    }
	    @Mock
	    List<String> mockedList;

	    @Test
	    public void whenUseMockAnnotation() {
	        mockedList.add("one");
	        verify(mockedList).add("one");
	        assertEquals(0, mockedList.size());
	 
	        when(mockedList.size()).thenReturn(100);
	        assertEquals(100, mockedList.size());
	    }
    }

但是代码的第一部分运行正常，尽管据我了解，两部分代码都在做相同的事情。

编辑后的堆栈跟踪：

java.lang.NullPointerException
    at com.foxminded.decoratortest.DecoratorTest.whenUseMockAnnotation(DecoratorTest.java:39)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    ...

请注意，由于您要求只返回翻译好的部分，我已经省略了代码中的重复部分以及堆栈跟踪中的重复信息。如果您需要更多内容或解释，请随时提问。

英文:

I'm figuring out how to work with Mockito and Junit and now testing some snippets. I don't understand why I have NPE in the following code after Mock annotation:

@RunWith(MockitoJUnitRunner.class)
public class MockitoTest{
    @Test
    public void whenNotUseMockAnnotation() {
        List mockList = mock(ArrayList.class);
    
        mockList.add(&quot;one&quot;);
        verify(mockList).add(&quot;one&quot;);
        assertEquals(0, mockList.size());
 
        when(mockList.size()).thenReturn(100);
        assertEquals(100, mockList.size());
    }
    @Mock
    List &lt;String&gt; mockedList;

    @Test
    public void whenUseMockAnnotation() {
        mockedList.add(&quot;one&quot;);
        verify(mockedList).add(&quot;one&quot;);
        assertEquals(0, mockedList.size());
 
        when(mockedList.size()).thenReturn(100);
        assertEquals(100, mockedList.size());
    }
}

But the first part of the code works fine, although as far as I understand both parts are doing the same.

EDITED:
the stack trace:

java.lang.NullPointerException
at com.foxminded.decoratortest.DecoratorTest.whenUseMockAnnotation(DecoratorTest.java:39)
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:564)
at org.junit.platform.commons.util.ReflectionUtils.invokeMethod(ReflectionUtils.java:675)
at org.junit.jupiter.engine.execution.MethodInvocation.proceed(MethodInvocation.java:60)
at org.junit.jupiter.engine.execution.InvocationInterceptorChain$ValidatingInvocation.proceed(InvocationInterceptorChain.java:125)
at org.junit.jupiter.engine.extension.TimeoutExtension.intercept(TimeoutExtension.java:132)
at org.junit.jupiter.engine.extension.TimeoutExtension.interceptTestableMethod(TimeoutExtension.java:124)
at org.junit.jupiter.engine.extension.TimeoutExtension.interceptTestMethod(TimeoutExtension.java:74)
at org.junit.jupiter.engine.execution.ExecutableInvoker$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:104)
at org.junit.jupiter.engine.execution.InvocationInterceptorChain.proceed(InvocationInterceptorChain.java:62)
at org.junit.jupiter.engine.execution.InvocationInterceptorChain.chainAndInvoke(InvocationInterceptorChain.java:43)
at org.junit.jupiter.engine.execution.InvocationInterceptorChain.invoke(InvocationInterceptorChain.java:35)
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$6(TestMethodTestDescriptor.java:202)
at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.invokeTestMethod(TestMethodTestDescriptor.java:198)
at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.execute(TestMethodTestDescriptor.java:135)
at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.execute(TestMethodTestDescriptor.java:69)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$5(NodeTestTask.java:135)
at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$7(NodeTestTask.java:125)
at org.junit.platform.engine.support.hierarchical.Node.around(Node.java:135)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$8(NodeTestTask.java:123)
at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.executeRecursively(NodeTestTask.java:122)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.execute(NodeTestTask.java:80)
at java.base/java.util.ArrayList.forEach(ArrayList.java:1511)
at org.junit.platform.engine.support.hierarchical.SameThreadHierarchicalTestExecutorService.invokeAll(SameThreadHierarchicalTestExecutorService.java:38)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$5(NodeTestTask.java:139)
at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$7(NodeTestTask.java:125)
at org.junit.platform.engine.support.hierarchical.Node.around(Node.java:135)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$8(NodeTestTask.java:123)
at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.executeRecursively(NodeTestTask.java:122)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.execute(NodeTestTask.java:80)
at java.base/java.util.ArrayList.forEach(ArrayList.java:1511)
at org.junit.platform.engine.support.hierarchical.SameThreadHierarchicalTestExecutorService.invokeAll(SameThreadHierarchicalTestExecutorService.java:38)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$5(NodeTestTask.java:139)
at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$7(NodeTestTask.java:125)
at org.junit.platform.engine.support.hierarchical.Node.around(Node.java:135)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$8(NodeTestTask.java:123)
at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.executeRecursively(NodeTestTask.java:122)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.execute(NodeTestTask.java:80)
at org.junit.platform.engine.support.hierarchical.SameThreadHierarchicalTestExecutorService.submit(SameThreadHierarchicalTestExecutorService.java:32)
at org.junit.platform.engine.support.hierarchical.HierarchicalTestExecutor.execute(HierarchicalTestExecutor.java:57)
at org.junit.platform.engine.support.hierarchical.HierarchicalTestEngine.execute(HierarchicalTestEngine.java:51)
at org.junit.platform.launcher.core.DefaultLauncher.execute(DefaultLauncher.java:229)
at org.junit.platform.launcher.core.DefaultLauncher.lambda$execute$6(DefaultLauncher.java:197)
at org.junit.platform.launcher.core.DefaultLauncher.withInterceptedStreams(DefaultLauncher.java:211)
at org.junit.platform.launcher.core.DefaultLauncher.execute(DefaultLauncher.java:191)
at org.junit.platform.launcher.core.DefaultLauncher.execute(DefaultLauncher.java:137)
at org.eclipse.jdt.internal.junit5.runner.JUnit5TestReference.run(JUnit5TestReference.java:98)
at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:41)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:542)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:770)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:464)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:210)

答案1

得分: 3

将以下内容翻译如下：

将

@RunWith(MockitoJUnitRunner.class)

替换为

@ExtendWith(MockitoExtension.class)

它的效果非常好。

@RunWith 用于 Junit4，而 @ExtendWith 用于 Junit5。

英文:

Replace

@RunWith(MockitoJUnitRunner.class)

With

@ExtendWith(MockitoExtension.class)

It works like a charm.

@RunWith is for Junit4 whereas @ExtendWith is for Junit5.

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