java - 从另一个类方法内部调用时无法正确模拟方法调用

Question

MyClass firstClass = PowerMockito.spy(new MyClass());

AnotherClass secondClass;
secondClass = PowerMockito.mock(AnotherClass.class);
PowerMockito.when(secondClass.anotherFunction(Mockito.any()).thenReturn(1);

int myInt = firstClass.myFunction();

if (myInt == 1) {
    System.out.println("true");
}

myFunction 调用 anotherFunction 并返回 anotherFunction 的结果。

但它并没有像我期望的那样返回 1 并打印 "true"，相反它仍在执行其真正的功能。

我在这里错过了什么？

Answer 1

An instance of AnotherClass is created inside myFunction then the instance is used to call secondClass.anotherFunction from inside myFunction.

没错。这意味着使用的是真实实例，而不是模拟实例。被测方法与依赖紧密耦合，因为它自己创建了一个真实的实例

public class MyClass {

    public int myFunction() {
        AnotherClass secondClass = new AnotherClass();

        int result = secondClass.anotherFunction(someValue);

        //...

        return result;
    }    
}

How can I use the mocked instance instead?

您要么重构以通过构造函数或方法参数注入(inject)第二个类，这是一个干净的代码设计，要么您使用 powermock 模拟第二个类的初始化，在我看来这是糟糕的设计。

@RunWith(PowerMockRunner.class)
@PrepareForTest(MyClass.class) //<-- you must prepare the class creating the new instance
public class MyClassTest {
    @Test
    public void test() {
        //Arrange
        int expected = 1;                          
        //Mock second class
        AnotherClass secondClass;
        secondClass = PowerMockito.mock(AnotherClass.class);
        PowerMockito.when(secondClass.anotherFunction(Mockito.any()).thenReturn(expected);

        //mocking initialization of second class withing first class
        PowerMockito.whenNew(AnotherClass.class).withNoArguments().thenReturn(secondClass);

        MyClass firstClass = new MyClass();

        //Act
        int actual = firstClass.myFunction();

        //Assert                
        assertEquals(expected, actual);
    }
}

引用 How to mock construction of new objects