# Possible Error In Tester::#UN3

**URL:** <https://forum.codecrafters.io/t/possible-error-in-tester-un3/15547>\
**Category:** Challenges\
**Tags:** challenge:shell\
**Created:** [November 18, 2025, 1:29pm UTC](https://forum.codecrafters.io/t/possible-error-in-tester-un3/15547 "2025-11-18T13:29:01Z")\
**Posts on this page:** 5\
**Page:** 1

<div class="post-metadata">

**Author:** ![brianobot](https://yyz1.discourse-cdn.com/flex003/user_avatar/forum.codecrafters.io/brianobot/32/20096_2.png) [@brianobot](https://forum.codecrafters.io/u/brianobot)\
**Post date:** [November 18, 2025, 1:29pm UTC](https://forum.codecrafters.io/t/possible-error-in-tester-un3/15547/1 "2025-11-18T13:29:01Z")

</div>

I’m stuck on Stage #UN3.

I’ve tried to test manually, and the redirections work as expected,

Here are my logs:

```auto
$ ls -1 nonexistent >> baz.md
ls: nonexistent: No such file or directory
$ ls
README.md app codecrafters.yml	tests.py your_program.sh
__pycache__ baz.md pyproject.toml
$ 

```

This shows that the file was created even when the command failed and that’s the expected behavior.

But in the tests, the testers passes one value and expects another, which feels like a simple typo

 ![Screenshot 2025-11-18 at 2.26.02 PM](https://canada1.discourse-cdn.com/flex003/uploads/codecrafters/original/3X/3/7/37899547b7105a01c92d9c12cb9f143cd7855dcf.png)

Am I missing something here? Here is a link to my Github Repository  
[https://github.com/brianobot/codecrafters-shell-python](https://github.com/brianobot/codecrafters-shell-python).

---

<div class="post-metadata">

**Author:** ![andy1li](https://yyz1.discourse-cdn.com/flex003/user_avatar/forum.codecrafters.io/andy1li/32/10_2.png) [@andy1li](https://forum.codecrafters.io/u/andy1li)\
**Post date:** [November 19, 2025, 2:09am UTC](https://forum.codecrafters.io/t/possible-error-in-tester-un3/15547/4 "2025-11-19T02:09:52Z")

</div>

Hey @brianobot, the issue stems from this line. Removing it should fix the problem:

 ![image](https://canada1.discourse-cdn.com/flex003/uploads/codecrafters/original/3X/b/6/b6e075699feb81f8e76ffec27ac7c6a4125bd992.png)

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<div class="post-metadata">

**Author:** ![brianobot](https://yyz1.discourse-cdn.com/flex003/user_avatar/forum.codecrafters.io/brianobot/32/20096_2.png) [@brianobot](https://forum.codecrafters.io/u/brianobot)\
**Post date:** [November 19, 2025, 6:27am UTC](https://forum.codecrafters.io/t/possible-error-in-tester-un3/15547/6 "2025-11-19T06:27:36Z")

</div>

That line is needed for binding the Tab key got autocompletion on macOS, the line above works for most other Oses

Reference to docs: [readline — GNU readline interface — Python 3.14.0 documentation](https://docs.python.org/3/library/readline.html)

 ![Screenshot 2025-11-19 at 7.26.54 AM](https://canada1.discourse-cdn.com/flex003/uploads/codecrafters/original/3X/3/4/34e5c643a157c9f7b9920388c9003c2327027824.png)

---

<div class="post-metadata">

**Author:** ![andy1li](https://yyz1.discourse-cdn.com/flex003/user_avatar/forum.codecrafters.io/andy1li/32/10_2.png) [@andy1li](https://forum.codecrafters.io/u/andy1li)\
**Post date:** [November 25, 2025, 12:18am UTC](https://forum.codecrafters.io/t/possible-error-in-tester-un3/15547/8 "2025-11-25T00:18:23Z")

</div>

There are two possible approaches here:

- **Conditionally apply the fix** : Detect the operating system and only include that line for macOS.
- **Install GNU Readline on macOS** to replace the `editline` library.

---

<div class="post-metadata">

**Author:** ![brianobot](https://yyz1.discourse-cdn.com/flex003/user_avatar/forum.codecrafters.io/brianobot/32/20096_2.png) [@brianobot](https://forum.codecrafters.io/u/brianobot)\
**Post date:** [November 25, 2025, 8:19am UTC](https://forum.codecrafters.io/t/possible-error-in-tester-un3/15547/9 "2025-11-25T08:19:53Z")

</div>

Wow! Thank you very much  
this actually worked