使用 PowerMock 模拟私有方法，但仍会调用底层方法

Question

我试图模拟一个进行 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sample code from another questions answer，虽然测试通过了，但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()，它会打印到我的控制台。

很有趣，如果我注释掉第一个assertThat，则测试通过。 ?:(

那么，我如何模拟一个私有方法以使其不被调用？

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( "\n>>> GAMBLE CALLED <<<\n" );
        PowerMock_Test.gambleCalled = true;

        return gamble;
    }
}   

^可以理解，因为我的工作区不支持JNDI，只有生产环境支持

% 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。

Answer 1

来自PowerMock Private Method Example：

@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：

@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。

Answer 2

艺术乙，

只需粘贴在我的 Eclipse IDE 中运行良好的完整代码。我只是改变了我在上一篇文章中所说的期望。祝你好运。

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.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());

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

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

        assertThat( PowerMock_Test.gambleCalled, is(false) );
        spy.meaningfulPublicApi();
        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( "\n>>> GAMBLE CALLED <<<\n" );
        PowerMock_Test.gambleCalled = true;

        return gamble;
    }
}   

Answer 3

艺术乙，

您确定您的代码不起作用（或）我在这里遗漏了什么吗？我只是按照 Mike 建议的方式将您的方法期望替换为以下方法，并且效果很好：

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

我从没用过 Powermockito，但以前用过很多次。

Answer 4

当您使用spy 构造一个模拟对象时，它是一个真正的半支持对象。我的猜测是摆脱spy。处理 pure 模拟对象。

Answer 5

以上方法都不适合我，因为我的私有方法无效。

有这样的设置：

public class MainClass {
    public void publicFunction () {
      this.privateFunction(Arg1.class arg1, Arg2.class arg2);
    }

    private void privateFunction(Arg1.class arg1, Arg2.class arg2){
       // who cares, I don't want any of this to go off
    }

}

唯一有效的是：

@Test
public void whocares() throws Exception {
   mainSpy = spy(mockedMainClassInstance);
   PowerMockito.doNothing().when(mainSpy, "privateFunction", mockedArg1, mockedArg2);
   mainSpy.publicFunction(mockedArg0, mockedArg1, mockedArg2);
   verifyPrivate(mainSpy).invoke("privateFunction", mockedArg1, mockedArg2);

}

那是私有函数中的代码停止触发的时候