Failed test case: Missing correct printed message.
Expected:
One copy of Brave New World checked out. There are now 3 copies available.,
but got:
an incorrect message
According to the screenshot you have shared regarding the message you are getting, please double check if your implemented code prints the expected message.
(Solution code removed, as posting it publicly is against the honour code of this community, regardless if it is correct or not. You can share the errors you get)
From what I understand from your screenshot, these are two separate assignment submissions. Once, you got 30/30, and the other time you got 20/30.
If you are worried about the overall grade, just know, your highest grade is always saved. You can get 30/30 once and get 0 later 10 times, your graded will always be saved as the highest you got. Which in this case, will be 30.