docs: Fix path for Elixir tests

[antedeguemon]

Description

Hey there!

This pull request fixes the Elixir tests paths in CircleCI guides to test/**/*_test.exs instead of lib/**/*_test.exs. It is a small mistake, but might save somelate-night debugging of anyone else out there. 🦉

Reasons

By default, ExUnit expects tests to be located at test/**/*_test.exs unless purposefully changed by developer.

If the incorrect path is used, then CircleCI pipelines won't find the project's tests. Depending on the setup, the pipeline might be wrongfully marked as passing even if the tests would fail if executed.

mix test

(..) loads up test/test_helper.exs and then, requires all files matching the test/**/*_test.exs pattern in parallel.

Source: Official Elixir docs

Additionally, the correct path can be confirmed by running mix new (..) to initialize an empty project boilerplate:

❯ mix new sanity_check
# ...
* creating lib
* creating lib/sanity_check.ex
* creating test
* creating test/test_helper.exs
* creating test/sanity_check_test.exs

Content Checklist

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• Break up walls of text by adding paragraph breaks.
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• Consider whether the content would benefit from more subsections (h2-h6 headings) to make it easier to consume.
• Check all headings h1-h6 are in sentence case (only first letter is capitalized).
• Include relevant backlinks to other CircleCI docs/pages.

[rosieyohannan]

Thank you so much for fixing this for us @antedeguemon!

[rosieyohannan]

🎉