Mockito - test method that picks between two implementations of interface

I have an interface -

Interface Intf {

     public void intfMethod();

}

and 2 classes A and B implementing it

I am testing below class using JUnit and Mockito -

class CUT {

    //Gets initialized as null
    private Intf i;

    //Gets autowired as object of A
    private Intf a;

    //Gets autowired as object of B
    private Intf b;

    public void myMethod(SomeClass param) {

             if(param.getCondition()) 
                  i = a;
             } else {
                  i = b;
             }

             i.intfMethod();
    }
}

How do I verify in my test that the intfMethod() of the correct implementation was called?