Requirements

bash and friends (diff, grep, cat)

(Failing) Unit Test

./unit_test.sh

./texttest_fixture.sh

Specify days:

./texttest_fixture.sh 30

Verify againt ThirtyDays/stdout.gr

./verify.sh

BTW, the script is a pure "function", so this works:

$ echo -e 'Aged Brie,3,5\nOther Item,4,5' |\
    ./gilded_rose.sh |\
    ./gilded_rose.sh |\
    ./gilded_rose.sh
Aged Brie,0,8
Other Item,1,2