Declarative java :)

FibTest.java

package com.myzone.nopebook;

import java.util.function.Function;

import static org.mockito.Matchers.*;
import static org.mockito.Mockito.*;

/**
 * Created by myzone on 12/3/13.
 */
public class FibTest {

    public static void main(String[] args) {
        Function<Integer, Integer> fib = mock(Function.class);

        doAnswer(invocation -> {
            Integer i = (Integer) invocation.getArguments()[0];

            return fib.apply(i - 2) + fib.apply(i - 1);
        }).when(fib).apply(any(Integer.class));
        doReturn(1).when(fib).apply(eq(1));
        doReturn(1).when(fib).apply(eq(2));

        System.out.println(fib.apply(10));
    }

}