使用 PowerMock 模拟私有方法，但仍会调用底层方法

问题描述

我正在尝试模拟一个进行 JNDI 调用的私有方法.当从单元测试中调用该方法时，它会引发异常^.我想模拟该方法以进行测试.我使用了 来自另一个问题的示例代码回答，当测试通过时，似乎仍然调用了底层方法.我在 doTheGamble() 方法中插入了一个 System.err.println()，它被打印到我的控制台.

I am trying to mock out a private method that is making a JNDI call. When that method gets called from a unit test, it throws an exception^. I would like to mock-out that method for testing purposes. I used the sample code from another questions answer, and while the test passes, it seems that the underlying method still gets called. I inserted a System.err.println() in the doTheGamble() method, and it gets printed out to my console.

很有趣，如果我注释掉第一个 assertThat，测试就通过了.?:(

Interesting enough, if I comment out the first assertThat, the test passes. ?:(

那么，我如何模拟一个私有方法以使其不被调用?

So, how do I mock out a private method so that it does not get called?

import static org.hamcrest.core.Is.is;
import static org.junit.Assert.assertThat;
import static org.mockito.Matchers.anyInt;
import static org.mockito.Matchers.anyString;
import static org.powermock.api.mockito.PowerMockito.when;
import static org.powermock.api.support.membermodification.MemberMatcher.method;

import java.util.Random;

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

@RunWith(PowerMockRunner.class)
@PrepareForTest(CodeWithPrivateMethod.class)
public class PowerMock_Test {

    static boolean gambleCalled = false; 

    @Test(expected = RuntimeException.class)
    public void when_gambling_is_true_then_always_explode() throws Exception {
        CodeWithPrivateMethod spy = PowerMockito.spy(new CodeWithPrivateMethod());

        when(spy, method(CodeWithPrivateMethod.class, "doTheGamble", String.class, int.class))
                .withArguments(anyString(), anyInt())
                .thenReturn(true);

/* 1 */ assertThat( PowerMock_Test.gambleCalled, is(false) );
        spy.meaningfulPublicApi();
/* 2 */ assertThat( PowerMock_Test.gambleCalled, is(false) );
    }
}


class CodeWithPrivateMethod {

    public void meaningfulPublicApi() {
        if (doTheGamble("Whatever", 1 << 3)) {
            throw new RuntimeException("boom");
        }
    }

    private boolean doTheGamble(String whatever, int binary) {
        Random random = new Random(System.nanoTime());
        boolean gamble = random.nextBoolean();

        System.err.println( "
>>> GAMBLE CALLED <<<
" );
        PowerMock_Test.gambleCalled = true;

        return gamble;
    }
}   

^可以理解，因为我的工作区不支持JNDI，所以只有生产环境支持

^ understandably, since my workspace does not support JNDI, only the production environment does

% 我正在使用所有库的最新版本，JUnit 4.10、Mockito 1.8.5、Hamcrest 1.1、Javassist 3.15.0 和 PowerMock 1.4.10.

% I am using the latest versions of all the library, JUnit 4.10, Mockito 1.8.5, Hamcrest 1.1, Javassist 3.15.0, and PowerMock 1.4.10.

推荐答案

来自 PowerMock 私有方法示例:

@RunWith(PowerMockRunner.class)
// We prepare PartialMockClass for test because it's final or we need to mock private or static methods
@PrepareForTest(PartialMockClass.class)
public class YourTestCase {
@Test
public void privatePartialMockingWithPowerMock() {        
    PartialMockClass classUnderTest = PowerMockito.spy(new PartialMockClass());

    // use PowerMockito to set up your expectation
    PowerMockito.doReturn(value).when(classUnderTest, "methodToMock", "parameter1");

    // execute your test
    classUnderTest.execute();

    // Use PowerMockito.verify() to verify result
    PowerMockito.verifyPrivate(classUnderTest, times(2)).invoke("methodToMock", "parameter1");
}

所以要将它应用到您的代码中，我认为它可能会变成:

So to apply this to your code, I think it might become:

@RunWith(PowerMockRunner.class)
@PrepareForTest(CodeWithPrivateMethod.class)
public class PowerMock_Test {
    @Test(expected = RuntimeException.class)
    public void when_gambling_is_true_then_always_explode() throws Exception {
        CodeWithPrivateMethod spy = PowerMockito.spy(new CodeWithPrivateMethod());

        PowerMockito.doReturn(true).when(spy, "doTheGamble", anyString(), anyInt());


/* 1 */ PowerMockito.verifyPrivate(spy, times(0)).invoke("doTheGamble", anyString(), anyInt());            
        spy.meaningfulPublicApi();
/* 2 */ PowerMockito.verifyPrivate(spy, times(2)).invoke("doTheGamble", anyString(), anyInt());            
    }
}

我只是在此处的编辑器中编写了代码.没有实际运行任何测试，并且在编写此代码时没有任何错误受到损害.

I just coded that in the editor here. No tests have actually been run, and no bugs have been harmed in the crafting of this code.

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