Nahhh. Been coding in many languages.

Why use IF EXPRESSION THEN BOOLEAN when all you need is EXPRESSION?

I think you're mis-reading the logs. There are two test cases right after each other, both of them are correct:

Test.assert_equals(score_hand(['A','A','A','J']), 13)
Test.assert_equals(score_hand(['A','2','A','9','9']), 22)

I have the same problem, and card was:
A
2
A
9
9

I use pritn to show what is in cards

You'll have to insert something into your code to see the parameters they're using for testing. Maybe print the inputs?
Regarding this test, if 13 is a possible total given the cards available, then you should return 13 and not 23, because the instrauctions say: "Return the highest score of the cards that is less than or equal to 21."

Please post the test case.

Use spoiler flag next time.

Because your post is visible in the home page if you don't mark it as having spoiler content, and your comment pretty much contained the solution.

@Steffan: dashboard is always acting weird with that. When you load it just after flagging, the comment is hidden, then for like 5-10minutes, it isn't anymore in the dashboard, than again.

Spoiler flag, please ^_^
EDIT: for some reason clicking spoiler doesn't make it disappear from the homepage?? (edit2: workin' now)

Please use spoler flag for things like this.