Not sure if anyone looks at feedback about these tests. I googled it and got quite a few hits that all say basically the same thing, but I figure the feedback forum is here for a reason, so.. here's entry number 1,866,234 in the "MR19 test is no fun" category.
Specifically, it requires extremely specific and perfectly executed skills and behavior that are not relevant to any other aspect of Warframe, ever, under any circumstance. I really enjoy most of the "stealthy" parts of the game (spy missions and floof hunting are great, even focus farming can be relaxing sometimes), but this is something else entirely. I'm fine just hanging out at MR18 forever, since there are no items restricted to higher ranks and I don't do a lot of trading, but it would be nice if this test were not a nigh-impossible slog.