SSLContext模拟行为不像预期的那样

Question

我有以下简单的类:导入javax.net.ssl.SSLContext；

public class AClass {
    public void someMethod() throws Exception {
        SSLContext context = SSLContext.getInstance("SSL");
        context.init(null, null, null);
    }
}

及其JUnit:进口javax.net.ssl.SSLContext；

import org.junit.Test;
import org.junit.runner.RunWith;
import org.mockito.Mockito;
import org.powermock.api.mockito.PowerMockito;
import org.powermock.core.classloader.annotations.PrepareForTest;
import org.powermock.modules.junit4.PowerMockRunner;

@RunWith(PowerMockRunner.class)
@PrepareForTest({ SSLContext.class })
public class ATest {
    @Test
    public void testSomeMethod() throws Exception {
        PowerMockito.mockStatic(SSLContext.class);
        SSLContext context = Mockito.mock(SSLContext.class);
        Mockito.when(context.getInstance("SSL")).thenReturn(context);
        new AClass().someMethod();
    }
}

下面的堆栈跟踪导致JUnit失败：

java.lang.NullPointerException
    at javax.net.ssl.SSLContext.init(Unknown Source)
    at random.AClass.someMethod(AClass.java:8)
    at random.ATest.testSomeMethod(ATest.java:20)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
    at java.lang.reflect.Method.invoke(Unknown Source)
    at org.junit.internal.runners.TestMethod.invoke(TestMethod.java:68)
    at org.powermock.modules.junit4.internal.impl.PowerMockJUnit44RunnerDelegateImpl$PowerMockJUnit44MethodRunner.runTestMethod(PowerMockJUnit44RunnerDelegateImpl.java:316)
    at org.junit.internal.runners.MethodRoadie$2.run(MethodRoadie.java:89)
    at org.junit.internal.runners.MethodRoadie.runBeforesThenTestThenAfters(MethodRoadie.java:97)
    at org.powermock.modules.junit4.internal.impl.PowerMockJUnit44RunnerDelegateImpl$PowerMockJUnit44MethodRunner.executeTest(PowerMockJUnit44RunnerDelegateImpl.java:300)
    at org.powermock.modules.junit4.internal.impl.PowerMockJUnit47RunnerDelegateImpl$PowerMockJUnit47MethodRunner.executeTestInSuper(PowerMockJUnit47RunnerDelegateImpl.java:131)
    at org.powermock.modules.junit4.internal.impl.PowerMockJUnit47RunnerDelegateImpl$PowerMockJUnit47MethodRunner.access$100(PowerMockJUnit47RunnerDelegateImpl.java:59)
    at org.powermock.modules.junit4.internal.impl.PowerMockJUnit47RunnerDelegateImpl$PowerMockJUnit47MethodRunner$TestExecutorStatement.evaluate(PowerMockJUnit47RunnerDelegateImpl.java:147)
    at org.powermock.modules.junit4.internal.impl.PowerMockJUnit47RunnerDelegateImpl$PowerMockJUnit47MethodRunner.evaluateStatement(PowerMockJUnit47RunnerDelegateImpl.java:107)
    at org.powermock.modules.junit4.internal.impl.PowerMockJUnit47RunnerDelegateImpl$PowerMockJUnit47MethodRunner.executeTest(PowerMockJUnit47RunnerDelegateImpl.java:82)
    at org.powermock.modules.junit4.internal.impl.PowerMockJUnit44RunnerDelegateImpl$PowerMockJUnit44MethodRunner.runBeforesThenTestThenAfters(PowerMockJUnit44RunnerDelegateImpl.java:288)
    at org.junit.internal.runners.MethodRoadie.runTest(MethodRoadie.java:87)
    at org.junit.internal.runners.MethodRoadie.run(MethodRoadie.java:50)
    at org.powermock.modules.junit4.internal.impl.PowerMockJUnit44RunnerDelegateImpl.invokeTestMethod(PowerMockJUnit44RunnerDelegateImpl.java:208)
    at org.powermock.modules.junit4.internal.impl.PowerMockJUnit44RunnerDelegateImpl.runMethods(PowerMockJUnit44RunnerDelegateImpl.java:147)
    at org.powermock.modules.junit4.internal.impl.PowerMockJUnit44RunnerDelegateImpl$1.run(PowerMockJUnit44RunnerDelegateImpl.java:121)
    at org.junit.internal.runners.ClassRoadie.runUnprotected(ClassRoadie.java:34)
    at org.junit.internal.runners.ClassRoadie.runProtected(ClassRoadie.java:44)
    at org.powermock.modules.junit4.internal.impl.PowerMockJUnit44RunnerDelegateImpl.run(PowerMockJUnit44RunnerDelegateImpl.java:123)
    at org.powermock.modules.junit4.common.internal.impl.JUnit4TestSuiteChunkerImpl.run(JUnit4TestSuiteChunkerImpl.java:121)
    at org.powermock.modules.junit4.common.internal.impl.AbstractCommonPowerMockRunner.run(AbstractCommonPowerMockRunner.java:53)
    at org.powermock.modules.junit4.PowerMockRunner.run(PowerMockRunner.java:59)
    at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:86)
    at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:459)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:675)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:382)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:192)

堆栈跟踪指向具有空指针的context.init(null, null, null);行。但是，当我调试(在Eclipse中)时，我可以清楚地看到context变量的值是一个Mock for SSLContext, hashCode: 1857173583。如果是模拟，那么像init()这样的void方法不应该做任何事情。那么，它为什么要抛出一个NullPointerException

Answer 1

查看API接口并对抛出NPE的init方法进行反编译签名，它显示为final，它是basic Mockito.mock()无法处理。

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另一方面，PowerMockito.mock()的javadoc读取：

org.powermock.api.mockito.PowerMockito 公共静态T模拟(类类型) 创建一个模拟对象，该对象支持对最终方法和本机方法的模拟。类型参数： mock模拟对象的类型 参数： 非匹配类型-模拟对象的类型 返回： 与模拟对象相对应。

所以，稍微改变一下你的测试应该能让它发挥作用：

@RunWith(PowerMockRunner.class)
@PrepareForTest({SSLContext.class})
public class ATest {
    @Test
    public void testSomeMethod() throws Exception {
        // create the mock to return by getInstance()
        SSLContext context = PowerMockito.mock(SSLContext.class);

        // mock the static method getInstance() to return above created mock context
        PowerMockito.mockStatic(SSLContext.class);
        Mockito.when(SSLContext.getInstance("SSL")).thenReturn(context);

        // invoke the object under test
        new AClass().someMethod();

        //TODO - add verifications / assertions
    }
}

更新：

因为您正在使用PowerMockRunner运行测试，所以您也可以替换

SSLContext context = PowerMockito.mock(SSLContext.class);

带着一块田

@Mock
private SSLContext context;

它也将由PowerMock处理(如果您只需要基本的mockito，则使用MockitoJUnitRunner )。