Test our popup
All of the methods are now in place for the pop-up window.
To test we will first refresh the page. After refreshing there will be no noticeable difference until we click on the add button in the toolbar. Do so now and see that the pop-up window opens centered on the page with the modal covering the background application. Now test the close button and re-open.
With the pop-up window open, your application should look like the following screenshot: