If a test taker loses power or internet, their information is saved.
Once a test taker submits an answer -it's saved in our private cloud and synced in our data store that physically spans across multiple time zones. So if they have submitted 10 answers we'll have the 10 save and sound.
The restart is a little trickier. For a short event on our end or (for example) if the test taker's Internet goes out - the login session is stored on the user's machine for about 45 minutes - during this time the test taker (most of time) should be able return back into the test without any time penalty. For a longer event - your test's Stop and Restart/Resume Number of Days Limit would be in effect.
In all instances there would be no time penalty and they would be be able to continue where they left off without any lost answers.