模拟静态类

Question

我在类中有一个实例化静态类实例并对其调用操作的方法。

public class SomeClass {
    public void someMethod() {
       MyClass.MyStaticClass myStaticClassInstance =
          new MyClass.MyStaticClass( arg1, arg2, arg3 );
       myStaticClassInstance.callSomeMethod();
    }
}
public class MyClass {
   public static class MyStaticClass {
      public MyStaticClass( Object arg1, Object arg2, Object arg3 ) {
      }
      public void callSomeMethod() {
      }
   }
}

如何模拟静态类

实例化，以便我可以在不通过静态类构造函数的情况下模拟callSomeMethod()？

Answer 1

你可以通过

模拟静态内部类的实例化来PowerMock做到这一点。这可以通过准备实际实例化静态内部类的类来完成，因此这里它将是您在其中定义了方法someMethod()的类。

假设someMethod()被定义为类MyOtherClass并且不返回任何内容，则测试类将如下所示：

@RunWith(PowerMockRunner.class) // The runner of PowerMock
@PrepareForTest(MyOtherClass.class) // the class to prepare
public class MyClassTest {
    @Test
    public void test() throws Exception {
        // The mock of your static inner class to return
        MyClass.MyStaticClass mock = Mockito.mock(MyClass.MyStaticClass.class);
        // Mock the call of callSomeMethod()
        PowerMockito.doAnswer(
            new Answer<Void>() {
                @Override
                public Void answer(final InvocationOnMock invocation) throws Throwable {
                    // Do something here as new implementation of callSomeMethod
                    System.out.println("My new Answer");
                    return null;
                }
            }
        ).when(mock).callSomeMethod();
        // Return your mock in case we instantiate MyClass.MyStaticClass in 
        // the prepared class with any arguments  
        PowerMockito.whenNew(MyClass.MyStaticClass.class)
            .withArguments(Matchers.any(), Matchers.any(), Matchers.any())
            .thenReturn(mock);
        // The code that will call someMethod
        MyOtherClass mc = new MyOtherClass();
        mc.someMethod();
    }
}

假设我的类MyClass如下所示：

public class MyClass {
    public static class MyStaticClass {
        public MyStaticClass(Object arg1, Object arg2, Object arg3) {
            System.out.println("Called constructor");
        }
        public void callSomeMethod() {
            System.out.println("callSomeMethod");
        }
    }
}

我的类MyOtherClass看起来像这样：

public class MyOtherClass {
    public void someMethod() {
        MyClass.MyStaticClass myStaticClassInstance = new MyClass.MyStaticClass(
            new Object(), new Object(), new Object()
        );
        myStaticClassInstance.callSomeMethod();
    }
}

如果我启动测试，我会得到预期：

My new Answer

而不是我默认应该得到的：

Called constructor
callSomeMethod

有关如何构造新对象的更多详细信息。

Answer 2

我写了一个更简单的工具，用于模拟通常"不可模拟"的东西 https://github.com/iirekm/misc/tree/master/ajmock

您的代码可能如下所示：

'

'' 公共类 MyClassTest {

@Test
public void test() throws Exception {
    MyClass.MyStaticClass mock = Mockito.mock(MyClass.MyStaticClass.class);
    when(() -> mock.callSomeMethod()).thenAnswer(() -> ...);
    when(() -> new MyClass.MyStaticClass(any(), any(), any())).thenReturn(mock);
    // The code that will call someMethod
    MyOtherClass mc = new MyOtherClass();
    mc.someMethod();
}

}

'

''