Full Keyboard Access can be tested in the simulator! So convenient! You can enable it from Accessibility's settings in the simulator. And from there, you can navigate your app by just using your computer's keyboard.

iPhone simulator shows how you can enable Full Keyboard Access by toggling the Full Keyboard Access switch in settings. Another simulator shows the Twitter app open on the Twitter Accessibility account. The focus is on the Following button, by selecting the tab key, the focus will jump to the next interactive element, in this case, the Followings of the account.