I am doing the shell challenge currently and encountered following bizarre test failure:
[tester::#NI6] Running tests for Stage #NI6 (Quoting - Single quotes)
[... cut for brevity ...]
[tester::#NI6] Writing file "/tmp/bar/f 58" with content "pineapple pear."
[tester::#NI6] Writing file "/tmp/bar/f 73" with content "pear banana."
[tester::#NI6] Writing file "/tmp/bar/f 73" with content "strawberry raspberry."
[your-program] $
[tester::#NI6] > cat '/tmp/bar/f 58' '/tmp/bar/f 73' '/tmp/bar/f 73'
[your-program] pineapple pear.strawberry raspberry.
[tester::#NI6] Expected: "pineapple pear.pear banana.strawberry raspberry."
[tester::#NI6] Received: "pineapple pear.strawberry raspberry."
[your-program] strawberry raspberry.
[your-program] $
[tester::#NI6] Received output does not match expectation.
[tester::#NI6] Test failed (try setting 'debug: true' in your codecrafters.yml to see more details)
Apparently the runner can create the same file name multiple times with different content. A check for uniquely generated file names on the runners side would most likely fix this.