#[cfg(test)] mod test_focus {
    use super::focus::*;
    #[test] fn test_focus () {

        struct FocusTest {
            focused: char,
            cursor: (usize, usize)
        }

        impl HasFocus for FocusTest {
            type Item = char;
            fn focused (&self) -> Self::Item {
                self.focused
            }
            fn set_focused (&mut self, to: Self::Item) {
                self.focused = to
            }
        }

        impl FocusGrid for FocusTest {
            fn focus_cursor (&self) -> (usize, usize) {
                self.cursor
            }
            fn focus_cursor_mut (&mut self) -> &mut (usize, usize) {
                &mut self.cursor
            }
            fn focus_layout (&self) -> &[&[Self::Item]] {
                &[
                    &['a', 'a', 'a', 'b', 'b', 'd'],
                    &['a', 'a', 'a', 'b', 'b', 'd'],
                    &['a', 'a', 'a', 'c', 'c', 'd'],
                    &['a', 'a', 'a', 'c', 'c', 'd'],
                    &['e', 'e', 'e', 'e', 'e', 'e'],
                ]
            }
        }

        let mut tester = FocusTest { focused: 'a', cursor: (0, 0) };

        tester.focus_right();
        assert_eq!(tester.cursor.0, 3);
        assert_eq!(tester.focused, 'b');

        tester.focus_down();
        assert_eq!(tester.cursor.1, 2);
        assert_eq!(tester.focused, 'c');

    }
}