docs: update styleguide.md with some prose on testing

[haakonvt]

Lets try to get it to flag redundant tests automatically 🤞

[gemini-code-assist]

Using Gemini Code Assist

The full guide for Gemini Code Assist can be found on our documentation page, here are some quick tips.

Invoking Gemini

You can request assistance from Gemini at any point by creating a comment using either /gemini <command> or @gemini-code-assist <command>. Below is a summary of the supported commands on the current page.

Feature	Command	Description

Customization

To customize Gemini Code Assist for GitHub experience, repository maintainers can create a configuration file and/or provide a custom code review style guide (such as PEP-8 for Python) by creating and adding files to a .gemini/ folder in the base of the repository. Detailed instructions can be found here.

Limitations & Feedback

Gemini Code Assist may make mistakes. Please leave feedback on any instances where its feedback is incorrect or counter productive. You can react with 👍 and 👎 on @gemini-code-assist comments. If you're interested in giving your feedback about your experience with Gemini Code Assist for Github and other Google products, sign up here.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 91.27%. Comparing base (bcc27ab) to head (afbdc97).
⚠️ Report is 2 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2423      +/-   ##
==========================================
- Coverage   91.28%   91.27%   -0.02%     
==========================================
  Files         192      192              
  Lines       26184    26184              
==========================================
- Hits        23903    23899       -4     
- Misses       2281     2285       +4     

see 4 files with indirect coverage changes

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.

[erlendvollset]

Not entirely true, there are edge cases that the automated tests don't cover. For example if an attribute is a union of multiple types, it will just test one of them, so there you should probably have some manual tests.

[haakonvt]

Right, yes 😢 We should really prioritize running it without a fixed seed...