Mockito: when Method A.a is called then execute B.b

Question

I'm using Mockito for JUnit tests. So there is a given class A that is used from the code i want to test:

class A{

    public A(){}

    public final String a(String x){
        return "A.a: " + x;
    }

}

and i want to replace the Method call A.a with another method call with the same arguments and same type of return value. As you can see, its not possible to override the method a by extending the class as it is final. So what i have now is another class B with the method B.b:

class B{

    public B(){}

    public String b(String x){
        return "B.b: " + x;
    }

}

Now i want to make sure every time when A.a is called from the code, the return value of B.b is used instead. Is there a possibility to achieve this with Mockito (something like Mockito.when(A.a(x)).thenReturn(B.b(x)); ) but with the same parameter x, without knowing the value of x?

Any help would be appreciated, thank you in advance!

What is the scenario you want to test ? Why A.a() is final ? and Why do you want to replace the call of A.a() ?. From what I understand you want to override A.a(), right ? — Adelin, Aug 23 '12 at 09:21
I'm testing an Android Library project (i use Robolectric as well, to be able to test Android projects). In this particular case i want to test a Database. The code calls a content resolver, the content provider is defined in the AndroidManifest.xml and i have not found a way to set the content provider programmatically as it is not loaded from the xml when running the tests. So i wanted the code to call the content provider instead of the content resolver. — user1448982, Aug 23 '12 at 10:40

score 22 · Answer 1 · answered Aug 23 '12 at 09:30

22

Well mockito mocks works by extending the class and overriding the method, which in your case is not possible on A.a(String). If you want this to happen you have to remove the final modifier.

Now assuming A.a(String) is not final, what you ask is completely doable with mockito:

given(mockA.a(anyString()).willAnswer(returnOfB(bInstance));

Answer<String> returnOfB(final B bInstance) {
    return new Answer<String>() {
         public String answer(Invocation invocation) {
             String arg = (String) invocation.getActualArguments()[0];
             return bInstance.b(arg);
         }
    };
}

Please note this answer has been written on a phone and might have typo, or wrong names, though you should get the idea of what should be done to achieve what you want.

Cheers

answered Aug 23 '12 at 09:30

bric3

40,072
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thank you, but its not a solution for me as i cant remove the final modifier. It is some code from the Android SDK. – user1448982 Aug 23 '12 at 10:44
3

@sergej-zagursky has the answer to get around the final modifier problem, but this one answers the gist of your original question. This is how you base your return value on the value of `x`. – jhericks Aug 23 '12 at 15:04
How do I import the "given"? – neves May 30 '17 at 15:24
@neves Use `org.mockito.BDDMockito.given` ;) – bric3 May 30 '17 at 15:49

score 3 · Accepted Answer · answered Aug 23 '12 at 09:27

3

It isn't possible to override final methods for Mockito-generated mocks, according to Mockito limits. But you can use Powermock to hack code at runtime so that Mockito can do its job.

answered Aug 23 '12 at 09:27

Sergej Zagursky

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3

This gets around the `final` problem and @brice's answer answers the gist of your original question. – jhericks Aug 23 '12 at 15:02

Simon Hellinger · Answer 3 · 2012-08-23T09:51:50.140

Basically I took your setup and wrote a Unit-Test with it. What popped up first was an error message that explicitly stated this:

org.mockito.exceptions.misusing.MissingMethodInvocationException: when() requires an argument which has to be 'a method call on a mock'.

And later in the trace it states that "you stub either of: final/private/equals()/hashCode() methods. Those methods cannot be stubbed/verified."

So according to Mockito you cannot stub final methods, and that's that.

Edit: So you have to either remove the final modifier or, in case you're stuck with this class as it is, find another way around it.

Mockito: when Method A.a is called then execute B.b

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