2019/02/04/mockito-doreturn-vs-thenreturn

[utterances-bot]

Mockito: doReturn vs thenReturn

In Mockito, you can specify what to return when a method is called. That makes unit testing easier because you don’t have to change existing classes. Mockito...

http://sangsoonam.github.io/2019/02/04/mockito-doreturn-vs-thenreturn.html

[asheCarry]

I spy an instance from applicationContext, doreturn when(instance).someVoidMethod(),but I find someVoidMethod had been called;
tradeBasicServiceSpy = Mockito.spy(applicationContext.getBean(ITradeBasicService.class));
Mockito.doThrow(OvsBusinessCheckedException.class).doNothing().when(tradeBasicServiceSpy).updateStatusAndVersionCompareStatusAndVersionById(
Mockito.anyLong(), Mockito.anyString(), Mockito.anyString(), Mockito.anyByte());

[SangsooNam]

@asheCarry First of all, I think it better to call 'spy' on the object you want to monitor directly. You called 'spy' on applicationContext.getBean(ITradeBasicService.class) rather than applicationContext. You might have an issue because you spy on the result of getBean.

If you spy on applicationContext, you can return a mock object when getBean(ITradeBasicService.class) is called. That mock object can throw an exception, which you wanted to do.

// Mock Service
service = Mockito.mock(ITradeBasicService.class);
Mockito.doThrow(OvsBusinessCheckedException.class).doNothing().when(service).updateStatusAndVersionCompareStatusAndVersionById(Mockito.anyLong(), Mockito.anyString(), Mockito.anyString(), Mockito.anyByte());

// Spy
context = Mockito.spy(applicationContext);

// Spy returns Mock Service
Mockito.doReturn(service).when (context).getBean(ITradeBasicService.class);

[asheCarry]

First,thanks for your answer.
My really question,I can not understand that when I use spy like #doReturn("foo").when(spy).get(0);# also throws IndexOutOfBoundsException ;
Now, I understand that Method of spy just adds proxy for the object from parameter,so when the object from parameter is a proxy essentially,doRetun().when(spyOfProxyObject).doSomething() also make A side effect.
So sorry for my lame English，I hope you can understand what I say;If you can,expect you can fix it。
Thanx again.

[SangsooNam]

@asheCarry
If the below code throws IndexOutOfBoundsException, I believe something is wrong.

doReturn("foo").when(spy).get(0);

Technically, this doesn't call the get method. This just configures what should be returned when get method with an argument 0 is called. By having this configure, this assertion passes. If there is no matched configuration, the method call hits the real implementation.

assertEquals("foo", spy.get(0));

[asheCarry]

@SangsooNam
`
@test
public void spyTest() {
// realTarget
List list = new LinkedList();

    MyProxyList handler = new MyProxyList(list);
    ClassLoader loader = list.getClass().getClassLoader();
    Class[] interfaces = list.getClass().getInterfaces();
    // proxy target
    List proxy = (List) Proxy.newProxyInstance(loader, interfaces, handler);
    // spy proxy
    List spy = Mockito.spy(proxy);
    // will run get() then throw java.lang.IndexOutOfBoundsException: Index: 0, Size: 0
    try{
        Mockito.doReturn("foo").when(spy).get(0);
    }catch (Exception e){
        Throwable cause = e.getCause().getCause();
        Assert.assertTrue(cause instanceof IndexOutOfBoundsException);
    }
}

class MyProxyList implements InvocationHandler {
    List target;

    MyProxyList(List target) {
        this.target = target;
    }

    @Override
    public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
        return method.invoke(target, args);
    }
}

`
doReturn("foo").when(spy).get(0) will throw IndexOutOfBoundsException

[asheCarry]

@SangsooNam
I resolved my problem by replace target object with the object come from spy;
So I can enjoy all functions from aop，and also not make relly rpc call method that I stub it

[SangsooNam]

@asheCarry
I don't have the full reason that you needed to spy the proxy. For the simple case, the below test works without throwing the exception.

@Test
public void doReturnWithSpyList() {
	List list = new LinkedList<String>();
	List spy = Mockito.spy(list);

	// This doesn't throw IndexOutOfBoundsException
	Mockito.doReturn("foo").when(spy).get(0);

	Assert.assertEquals("foo", spy.get(0));
}

And, when I run your test, it doesn't work and fails with Mockito cannot mock/spy because : final class. Maybe there is some other thing and I wanted to share my runs.

[asheCarry]

@SangsooNam
InvocationHandler the full name is org.springframework.cglib.proxy.InvocationHandler；
I heared can mock or spy final class on higher version of Mockito,just heared but not test it;
The primary reason of I want to spy a proxy instance is that which code is needed to be tested uses proxy instance not origin object . Proxy intance can enhance origin object, like adding transaction for some method by use annotation @transaction