Those "tests" are virtually useless.

Those "isolation tests" where they put people into isolated places like the Canadian Arctic or that place on the mountain in hawaii for months at a time to see how they handle the isolation will NOT really show the effects on the explorers.

1. They are still living in a one G gravity field. That is much better for human health than zero G or the very low gravity of Mars. The gradual health decline of the low or no gravity will mess up the astronauts in ways these tests cannot show.

2. They KNOW they have an out, that if push really comes to shove they have the option of leaving. Just KNOWING YOU HAVE THAT OPTION will be very emotionally soothing to the people involved, its like a placebo effect. Placebo effect is VERY strong. In the movie PUNISHER Thomas Jane tricked his victim into thinking he was being cooked alive but in reality it was just a popsickle being rubbed on his back and the man actually WENT INTO PHYSICAL SHOCK. Doctors have done experiments with placebos too. They also know they are in no significant danger and being "safe" on Earth compared to the dangers of space will also put them more at ease emotionally.

3. Even then 4 of the 6 isolated astronauts failed to make it, and the actual mission will be much more stressful, this is NOT boding well.... That being said EVEN IF THEY PASSED WITH FLYING COLORS it does not at all mean they would last the same way on a REAL EFFING MISSION as I explained in parts 1 and 2 above.