如何使用 PowerMock 模拟被测 Class 以外的另一个 Class 的私有方法？

Question

我有一个 class，我想用调用另一个 class 的私有方法的 public 方法对其进行测试。当我尝试调用相同 class 的私有方法时，一切正常。当我尝试模拟另一个从被测 class 调用的私有方法时出现问题。以下是测试的代码示例 class.

@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();
    }
}

以下是测试中 class 的代码示例

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 class 的代码示例，它从被测 class 中调用

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 Class 的 doTheGamble() 方法以使其始终 return 为真？

Answer 1

这里的问题是，虽然您在测试中创建了 CodeWithAnotherPrivateMethod 的间谍，但在 CodeWithPrivateMethod 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();

为避免这种情况，您可以在创建新实例时强制 return 您的 CodeWithAnotherPrivateMethod 模拟。您可以使用 PowerMockito whenNew() 功能来执行此操作。

示例：

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

最后，你的测试应该是这样的：

@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();
}

希望对您有所帮助。

如何使用 PowerMock 模拟被测 Class 以外的另一个 Class 的私有方法？

How to mock private method of another Class other than the Class under test using PowerMock?

java

testing

unit-testing

mockito

powermock