Thanks for the advice, i'm new on this website.
What is considered a spoiler?
I thought about it before posting it but since the solution was provided, i didn't think it could be an issue, i guess i was wrong :p

Please use a spoiler flag, comments are visible by default to everyone (I put the flag for you this time).

I tested with your code.
It calculates result at the end of all tests (and not after each test).

If you get this

   Calculating errors...
     Value is not what was expected
     Value is not what was expected

it means, that your predictions are not accurate enough.

SPOILER FLAG!! x/

Can you show me your code?

I checked it again, still the same answer: " More testing" ---> "Calculating errors..." ---> "Value is not what was expected"

I made a little change. Try again.

Hi,
I didn't understand what the prediction model you meaning.
Simple linear regression doesn't pass the tests (it pass small, medium and bigdata tests, but not " More testing"), so I don't understand what the model I have to use
Thanks