Thanks Matt, that I'll do :)

This test is super easy in Ruby, nontheless the submit tests do not pass.

It prints

{"stdout":"Basic tests\nunique letters\nTest Passed: Value == [\"a\"]\nTest Passed: Value == [\"ab\", \"ba\"]\nTest ...

Any clue ?

Thank you very much ! I tried it before but since I am a noob I was not very confident.
So I tried again with a deeper copy (using mapito = minemap.map { |e| e.dup } in Ruby) and I worked.

Still... it is the first time it happens. I have no idea how I can avoid this in the future.

I am pretty sure my fairly stupid algorithm works but it seems to transform the value of the minemap for the next run of the function.
So it works each first time the minemap changes in the tests, but the second it uses the changed map.

I am new to programming and this does not make any sense to me... Any help or clue ?

I am surprised this worked in the tests. Well done!