I did two of the McKinsey PSTs (A and B, saving C for later) and did one from Igotanoffer. My impression is that the Igotanoffer test is a bit easier compared to the McKinsey PSTs. My impression might be biased though, because of my improvement.
Hello! Personally, having done all of them, I believe they are a very good "copy". However, test are always changing to incorporte new concepts, so they don´t become obsolete (and copied by the webpages), so don´t be surprised if the real one at the McK offices is slightly different (which doesn´t mean more difficult)
Cheers!
We explain and give tips on how to understand and analyze graphs, charts and data presented by interviewer to candidates in case interviews.
QuizTop tier consulting firms have started using PSTs to test for in-depth analytical skills needed to be successful as a consultant on a day-to-day basis.
All major firms like McKinsey, BCG and Bain use tests to assess a candidate's analytical skills. However the design of those tests can differ a lot.
GOT - Got your Offer Training 
Prep Guide for McKinsey PST by PrepLounge 
McKinsey PST #3 by Riccardo 
McKinsey PST #2 by Gaurav 
McKinsey PST #1 by PrepLounge 
