如何使用PowerMock模拟测试类以外的另一个类的私有方法？

Question

@RunWith(PowerMockRunner.class)
@PrepareForTest({CodeWithPrivateMethod.class,CodeWithAnotherPrivateMethod.class})
public class CodeWithPrivateMethodTest {

    @Test
    public void when_gambling_is_true_then_always_explode() throws Exception {
        CodeWithPrivateMethod spy = PowerMockito.spy(new CodeWithPrivateMethod());
        CodeWithAnotherPrivateMethod codeWithAnotherPrivateMethod = PowerMockito.spy(new CodeWithAnotherPrivateMethod());      

        /*when(codeWithAnotherPrivateMethod, method(CodeWithAnotherPrivateMethod.class, "doTheGame", String.class))
                .withArguments(anyString())
                .thenReturn(true);*/

        PowerMockito.when(codeWithAnotherPrivateMethod, "doTheGame", anyString()).thenReturn(true);
        //PowerMockito.doReturn(true).when(codeWithAnotherPrivateMethod, "doTheGamble", anyString(),anyInt());

        spy.meaningfulPublicApi();
    }
}

import java.util.Random;

public class CodeWithPrivateMethod {

    CodeWithAnotherPrivateMethod anotherPrivateMethod = new CodeWithAnotherPrivateMethod();

    public void meaningfulPublicApi() {
        if (anotherPrivateMethod.doTheGame("Whatever")) {
            System.out.println("kaboom");
        }
    } 
}

下面是从测试中的类调用的类的代码示例

import java.util.Random;

public class CodeWithAnotherPrivateMethod {

    public boolean doTheGame(String string) {
        return doTheGamble("Whatever", 1 << 3);
    }

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

所以我的问题是如何成功地模拟CodeWithAnotherPrivateMethod类的doTheGamble（）方法，使其始终返回true？

Answer 1

这里的问题是，尽管您在测试中创建了CodeWithanOtherPrivateMethod的间谍，但在CodeWithanOtherPrivateMethod中创建了CodeWithanOtherPrivateMethod的新实例。所以，实际上你没有使用你的模拟。

CodeWithAnotherPrivateMethod anotherPrivateMethod = new CodeWithAnotherPrivateMethod();

为了避免这种情况，可以在创建新实例时强制返回CodeWithAnotherPrivateMethod模拟。您可以使用PowerMockitoWhennew()功能来完成此操作。

示例：

PowerMockito.whenNew(CodeWithAnotherPrivateMethod.class).withAnyArguments().thenReturn(codeWithAnotherPrivateMethod);

@Test
public void when_gambling_is_true_then_always_explode() throws Exception {
  // Spy CodeWithAnotherPrivateMethod and force return true when doTheGamble is called
  CodeWithAnotherPrivateMethod codeWithAnotherPrivateMethod = PowerMockito.spy(new CodeWithAnotherPrivateMethod());
  PowerMockito.doReturn(true).when(codeWithAnotherPrivateMethod, "doTheGamble", Mockito.anyString(), Mockito.anyInt());
  // Return your mock when a new instance of CodeWithAnotherPrivateMethod is created.
  PowerMockito.whenNew(CodeWithAnotherPrivateMethod.class).withAnyArguments().thenReturn(codeWithAnotherPrivateMethod);

  CodeWithPrivateMethod spy = PowerMockito.spy(new CodeWithPrivateMethod());
  spy.meaningfulPublicApi();
}