fn modify_domain() {

    let a = Name::UserName(String::from("a"));

    let d1 = Domain::IntDomain(vec![Range::Bounded(1, 3)]);

    let d2 = Domain::IntDomain(vec![Range::Bounded(1, 2)]);

    let mut symbols = SymbolTable::new();

    symbols

        .insert(Rc::new(Declaration::new_var(a.clone(), d1.clone())))

        .unwrap();

    let m = Model::new(Rc::new(RefCell::new(symbols)), vec![], Default::default());

    assert_eq!(&m.symbols().domain(&a).unwrap(), &d1);

    let mut decl_a = m.symbols().lookup(&a).unwrap();

    Rc::make_mut(&mut decl_a).as_var_mut().unwrap().domain = d2.clone();

    m.symbols_mut().update_insert(decl_a);

    assert_eq!(&m.symbols().domain(&a).unwrap(), &d2);

}