How to check if a varchar contains an upper case char in postgreSQL?

I have another Question comming up, while solving some problems with postgreSQL. Is there any option, to check (in a check statement), if a varchar() contains an upper case character? (I want that my table only holds Strings with at least one upper case letter.) Thats how my table look:

CREATE TABLE test(
    id integer PRIMARY KEY,
    code varchar(255) not null,
    CHECK ((char_length(code) >= 10) && check for upperCase?)
);

Does anyone have a tip how to solve this? Regards, Lukas

Answer

Make sure there are at least one non-lower case character:

CHECK ((char_length(code) >= 10) and code <> lower(code))