This app search for an early driving test in UK.
Basically, you can put the max date that want to get test, then the app will search the time frequency that you have decided before and the area you choose. When it finally find an available test date for you the app keep it for 15mins for you unless you book or cancel it. To find an available test, the app needs to be open and on the foreground. To find an available test might take hours or days depends on where you looking for and how soon you looking for.