FYI:
1. If I click the piano keyboard, it brings up a popup window of a piano keyboard with playable notes, I found you have to click the icon that looks like a stacked pair of horizontal slide switches, and then where it says INSTRUMENT, you have to click on that and then select UKULELE. You might want to correct your instructions above.
2. In doing the UKULELE note test, it's not clear what you are supposed to do, maybe one line of instructions like 'Select the NAME of the fretted NOTE' or something above the fretboard graphic? I got this by trial and error and will be frustrating to a newbie.
3. There's not a great deal of entropy in the notes shown on the fretboard for you to identify, and it seems like I'm getting lots of repeat notes shown - maybe you can store the previously selected notes from the fretboard into an array (or other list), and then before randomly selecting another, make sure it was not one of the previously shown 10 or so notes, otherwise it does not provide much of a challenge.
Aside from the above, this is a great first start and should be quite useful for other folks to learn the names of the notes.
I did not yet try the guitar, piano or other instruments yet, mostly because I did not have lots of time, but I would like to come back later and see how they work compared to the ukulele test.
Thanks for sharing this, we need good musical tools like this.