Parallelize rspec tests

[akarki2005]

Proposed Changes

Adds the parallel_tests gem to run RSpec tests in parallel, reducing CI test suite runtime. Each parallel worker gets its own isolated test database using the TEST_ENV_NUMBER environment variable. System tests continue to run sequentially as they require a browser.

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📦 Dependency update (change that updates a dependency)
🔧 Internal (change that only affects developers or continuous integration)	X

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[akarki2005]

Hi @david-yz-liu, I'm seeing that the CI run is failing due to the parallel_tests gem not getting installed properly - I made a commit to try and address this, but I think the bundle cache is stale, and I'm unable to change Gemfile.lock to re-trigger it. Are you able to clear the Actions cache for my PR? Thanks :)

[david-yz-liu]

@akarki2005 I removed the gem cache and re-ran the tests. It looks like the gem installed correctly, but there's an issue with bundler using parallel_tests. See my comments for a suggested fix.

[coveralls]

Coverage Report for CI Build 27071576024

Coverage remained the same at 90.202%

Details

• Coverage remained the same as the base build.
• Patch coverage: No coverable lines changed in this PR.
• No coverage regressions found.

Uncovered Changes

No uncovered changes found.

Coverage Regressions

No coverage regressions found.

---

Coverage Stats

Relevant Lines:	50140
Covered Lines:	46213
Line Coverage:	92.17%
Relevant Branches:	2230
Covered Branches:	1026
Branch Coverage:	46.01%
Branches in Coverage %:	Yes
Coverage Strength:	126.26 hits per line

---

💛 - Coveralls

[david-yz-liu]

@akarki2005 nice work! In addition to the inline comments I left, I think we can improve the GitHub Actions part a bit. Take a look at https://github.com/grosser/parallel_rails_example/blob/master/.github/workflows/test.yml, and in particular the store-runtime action. I think the goal of that is to cache the test logs so that the test parallelization is more balanced in future runs.

[david-yz-liu]

@akarki2005 the changes look good to me (and do seem to faithfully follow the parallel_tests example) but in the GitHub Actions flow, it looks like the tasks that involve deleting the cache are failing.

But also in the most recent test run I think there's an issue with redis as well with parallelization: https://github.com/MarkUsProject/Markus/actions/runs/27071576024/job/79960812268.