Play level difficulty for testing

To test the beta releases, I am currently playing at "easy" level, most to the time. And, as it is convenient, I suppose that many other testers are playing at low levels too.

So I have a question : should I test also with other difficulty levels ? Do the difficulty levels have an impact on a mission flow or paths ?

Would be a mess if the hard levels has some troubles left...

Yes you should test as many difficulty levels as possible

I'm currently planning on multiple play-throughs when the last bunch of mission related issues are solved so far. I'll play on different difficulties to check the balancing in a "normal" playing experience.