Key points:

Trying out your app after adding new features might be the most rewarding part of your development, especially when everything works perfectly the first time… which is to say: almost never!

Usually, you need to debug and fine-tune your code several times before it works exactly as you want. But remember: you really learn to code by trial and error. If something's wrong, you have several tools at your disposal, but arguably, your first stop should be a good use of breaking points to check what's really happening with your code.

Solution:

Try adding new items in the Items screen, then edit them several times. Try adding unexpected values and see how your app behaves.

Try also deleting items by swiping right and left.