Students will only need to undertake this additional step, which will involve "a nominal fee":
"if they wish to pursue Udacitiy's "official credential and be part of [its] job placement program."
Including an extra final test overcomes one of problems faced by online education — was it really the student who's name appears on the certificate that completed the course and took the test?
Was it that student's own unaided work?
By going to a Pearson Vue testing center your identity can be checked. And by sitting a test your knowledge can be established. However, as the first round of tests for Udacity courses are only 90 minutes, with a multiple choice format and no programming they are not a substitute for the course assessment that currently takes place — and, of course, this is not the intention. The idea is that your identify is checked and the fact that you do know enough for it to be reasonable that you actually took the more difficult online exam is the rational.