I'm making a web application using flask framework. To display a web page using flask, I use a render_template() function. For example:
@app.route('/restaurants/<int:restaurant_id>/')
def restaurantMenu(restaurant_id):
    try:
        # pdb.set_trace()
        session = get_session()
        restaurant = session.query(Restaurant).filter_by(id=restaurant_id).one()
        if restaurant is not None:
            menu_items = session.query(MenuItem).filter(
                  MenuItem.restaurant_id == restaurant.id
            )
        session.close()
        if menu_items is not None:
            return render_template('menu.html', restaurant=restaurant, items=menu_items)
    except NoResultFound:
        return render_template('error.html', error_message='No such restaurant id.')
And
@app.route('/')
def welcomePage():
    return render_template('index.html')
How do I write test cases for functions like these? I'm new to testing so I wanted to write test cases for my code.