Mock Simple example

public class SimpleMock {
    private static Calc calc;

    @BeforeClass
    public static void setUpClass() {
        calc = mock(Calc.class);
        when(calc.sum()).thenReturn(40);
    }

    @Test
    public void testSum() {
        assertEquals(40, calc.sum());
    }
}




class Calc {
    private int first;
    private int second;

    Calc(int first, int second) {
        this.first = first;
        this.second = second;
    }

    int sum() {
        return first + second;
    }

}