PowerMockito whenNew 对多层传递依赖类打桩不生效问题排查

Class A {
  someMethod() {
    B b = new B();
    b.someMethod();
  }
}

Class B {
  String someMethod() {
    C c = new C();
    return c.someMethod();
  }
}

Class C {
  String someMethod() {
    D d = new D();
    return d.getId()
  }
}

Class D {
  getId() {
    return "id123";
  }
}

对应测试代码如下：

@RunWith(PowerMockRunner.class)
@PrepareForTest({A.class, B.class, C.class})
MyTest {
  public void basicTest() {
    D mockDClass = mock(D.class);
    when(mockDClass.getId()).thenReturn("mockedId");
    PowerMockito.whenNew(D.class).withAnyArguments().thenReturn(mockClass);
  }
}

• 测试预期：执行后返回打桩的"mockedId"
• 实际结果：程序走入D的真实方法，打桩完全没有生效

疑问点：whenNew是不是仅对被测类自身内部new的对象生效，无法覆盖多层传递调用链中其他类内部new的对象？

为定位问题，编写了和上述业务逻辑完全一致的最小复现模块开展测试：

复现模块业务实现代码 #

public class A {
  public String someMethod() {
    B b = new B();
    return b.someMethod();
  }
}

public class B {
  public String someMethod() {
    C c = new C();
    return c.someMethod();
  }
}

public class C {
  public String someMethod() {
    D d = new D();
    return d.getId();
  }
}

public class D {
  public String getId() {
    return "id123";
  }
}

复现模块测试代码 #

import junit.framework.TestCase;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.powermock.core.classloader.annotations.PrepareForTest;
import org.powermock.modules.junit4.PowerMockRunner;

import static org.mockito.Mockito.*;
import static org.mockito.Mockito.mock;

@RunWith(PowerMockRunner.class)
@PrepareForTest({A.class, B.class, C.class})
public class ATest extends TestCase {
  @Test
  public void mockTest() {
    D mockD = mock(D.class);
    when(mockD.getId()).thenReturn("this is from mock");
    PowerMockito.whenNew(D.class).withAnyArguments().thenReturn(mockD);
    A a = new A();
    System.out.println(a.someMethod());
  }
}

复现结果 #

运行上述最小测试模块时，打桩逻辑却能正常生效，测试输出结果如下：

该结果说明正式业务测试用例存在配置问题，但暂时无法定位具体故障点。

内容的提问来源于stack exchange，提问作者Mohammed