State management

#[cfg(test)]
mod test_state{
    use std::cell::RefCell;

    use crate::State;

    #[test]
    fn set_state() {
        let a:State<i32> = State::default();    
        let b:State<i32> = State{data:Box::new(RefCell::new(200))};
        let b_state = b.get_state();    
        a.set_state(100);
        b.set_state(100);
        assert_eq!(a,b);
        &a.set_state(1000);
        assert_ne!(a.get_state(),b.get_state());
        
    }
}