    @Test
    public void testSubstr_3args() {

        System.out.println("substr");
        String str = "Juan Perez Benitez";
        int start = 5;
        int charactersReturned = 5;
        String expResult = "Perez";
        String result = Strings.substr(str, start, charactersReturned);
        assertEquals(expResult, result);
        
        start = 5;
        charactersReturned = 50;
        expResult = "Perez Benitez";
        result = Strings.substr(str, start, charactersReturned);
        assertEquals(expResult, result);
        
        str = null;
        expResult = null;
        result = Strings.substr(str, start, charactersReturned);
        assertEquals(expResult, result);
    }