[FIXED] How to mock a method which is outside the test class?

Issue

My code:

class C:

public class C{
    public int methodC(){
        return 1000;
    }
}

class B:

public class B{
    private static C c;
    public static int methodB(){
        int b = c.methodC();
        return b;
    }
}

class A:

public class A {
    public int methodA(){
        int a = B.methodB();
        return a;
    }
}

class TestA:

class TestA{

    @InjectMocks
    A a;
    @Mock
    C c;
    public void testMethodA(){
        when(c.methodC()).thenReturn(5);
        int result = a.methodA();
        assertEquals(result, 5);
    }
}

Even I mock c.methodC(), the methodC call in methodB returns null.

How can I mock the methodC call?

I cannot alter the source code but to do changes only in TestA class Also I cannot use PowerMockito too.

Solution

Here is a way to make it work using your constraints:

    A a = new A();
    C c = Mockito.mock(C.class);
    
    @Test
    public void testMethodA(){
        try {
            Field c = B.class.getDeclaredField("c");
            c.setAccessible(true);
            c.set(null, this.c);
        } catch (Exception e) {
            e.printStackTrace();
        } 
        Mockito.when(c.methodC()).thenReturn(5);
        int result = a.methodA();

        assertEquals(result, 5);       
    }

Answered By - jnorman