Warframe Mastery Rank Test Guide (Including MR30) | Warframe Wiki
Mastery Rank 28 - The Daily SPUF
Noob advice : don't do mastery rank test while a warframe update is pending. You won't be able to do it until you restart the client, and if you click to do
The Stream Team: Facing Warframe's Mastery Rank test | Massively Overpowered