Receiving an email inviting to do a personality test does indeed mean you passed that test day. However, it has been known on some occasions (evidence in this thread) that people CAN fail the online personality questionaire. So choose carefully, but above all honestly. You'll have at least two, if not more personality-style tests in the later stages, and they DO pick up on differences, no matter how minor. Usually these can be explained by talking to you in person, but often massive clashes mean an automatic "fail", so I've been told by HR.