Mocking final class with parameterized constructor

Question

I have a final class as below

public  class firstclass{

   private String firstmethod(){

       return new secondclass("params").somemethod();

}

}


public final class secondclass{

   secondclass(String params){

        //some code

}

public String somemethod(){

         // some code 
        return somevariable";
}
}

I have to here test first class so I have mocked this as below

secondclass classMock = PowerMockito.mock(secondclass .class);
        PowerMockito.whenNew(secondclass .class).withAnyArguments().thenReturn(classMock);
Mockito.doReturn("test").when(classMock).somemethod();

But it is not mocking as I expected can anyone help me?

Why would you mock a final class? If it's final, it's not meant to be used that way. — Louis Wasserman, Nov 02 '16 at 05:08
I have to test firstclass firstmethod. In that there is a call for secondclass somemethod which returns somevariable so I mocked that to return test value — Reddevil, Nov 02 '16 at 05:18
Then you should design the first class to accept an interface. If your first class is calling a final class, that's it, you can't change it. — Louis Wasserman, Nov 02 '16 at 05:19
No i can't change the code. So there is no way to mock that? — Reddevil, Nov 02 '16 at 05:21
No, there is no way for you to change that unless you change the code. The smallest possible unit under test possible in such a case is `firstclass` **and** `secondclass` as a union. — SpaceTrucker, Nov 02 '16 at 07:34

score 0 · Answer 1 · answered Nov 02 '16 at 10:39

The method firstclass.firstmethod() is private method. So try to test this method through public method in which it is getting called.
You can mock SecondClass and its final method using @RunWith(PowerMockRunner.class) and @PrepareForTest(SecondClass.class) annotations.

Please see below the working code:

import org.junit.After;
import org.junit.Before;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.mockito.Mockito;
import org.powermock.api.mockito.PowerMockito;
import org.powermock.core.classloader.annotations.PrepareForTest;
import org.powermock.modules.junit4.PowerMockRunner;

@RunWith(PowerMockRunner.class)
@PrepareForTest(SecondClass.class)
public class FirstClassTest{


    @Before
    public void init() {

    }

    @After
    public void clear() {

    }

    @Test
    public void testfirstmethod() throws Exception{

        SecondClass classMock = PowerMockito.mock(SecondClass.class);
        PowerMockito.whenNew(SecondClass.class).withAnyArguments().thenReturn(classMock);
        Mockito.doReturn("test").when(classMock).somemethod();

        new FirstClass().firstmethod();
    }
}

Libraries used:

Mocking final class with parameterized constructor

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