b1az
Coworker and I are at an impasse and would appreciate the community’s vote to resolve it. 
--trace option in a CI environment (GitHub)?- Yes,
--traceoption in a CI environment has its uses. - No,
--traceoption in a CI environment makes no sense.
Elixir’s test-runner has a --trace option which does the following:
- it discards all of Elixir’s concurrency abilities and (slowly) runs everything sequentially, one-by-one
- it prints the test-names (here, here, etc.), even the passing ones. (The failed tests are, of course, always printed, even without
--trace.) - sets the test-timeout to
:infinity. It’s tracing, so this is expected/welcome (in dev/local environment). But not desired in a CI env as it can blow up the bill/costs.
Here’re coworker and my positions:
- Coworker’s argument for tracing is effectively the 2. above. In his words, it “gives a better visual understanding which tests are running”.
- My position against it are that:
- Not only are downsides of 1. and 3. not worth it, but one can also
- just look at the test file to see which tests are running. Moreover, one shouldn’t even care about the names of the passing tests, abiding by the Rule of Silence.
Where Next?
Trending in Discussions
Other Trending Topics
Latest on Elixir Forum
Sponsor Spotlight
Error tracking, logs, APM, uptime and cron monitoring in one dev-friendly platform. Find and fix problems before your users notice.
Categories:
Sub Categories:
Forums
Popular Tags
- #ecto
- #liveview
- #troubleshooting
- #learning-elixir
- #library
- #deployment
- #erlang
- #testing
- #genserver
- #mix
- #absinthe
- #remote-other
- #otp
- #plug
- #how-to-question
- #macros
- #postgres
- #elixirconf
- #channels
- #exunit
- #discussion
- #code-sync
- #podcasts
- #javascript
- #onsite
- #dialyzer
- #docker
- #authentication
- #umbrella
- #full-time-contract
- #podcasts-by-brainlid
- #ai
- #ecto-query
- #elixirconf-us
- #blog-post
- #elixir-ls
- #phoenix_html
- #iex
- #graphql
- #genstage
- #websockets
- #supervisor
- #advent-of-code
- #distillery
- #processes
- #elixirconf-eu
- #api
- #forms
- #metaprogramming
- #hex
Our Sponsors
Build Elixir applications with speed and confidence.
Supporting innovation across the BEAM ecosystem.
We build reliable cloud platforms for business-critical systems.
Error tracking, logs, uptime, and Just Enough APM. Built for developers.
Elixir, Erlang & BEAM conferences from Code Sync - join us in 2026!
Practical resources that improve the lives of professional developers.
Master modern tools, write cleaner code, and tackle real-world challenges.
Bringing learning, work and compliance together since 1987.
The team behind Membrane, Popcorn, LiveDebugger. Available for hire.
Courses that'll move you from confusion to "Aha, now I get it!"
Showing Posts 1 to 4- Show Best Posts
- Show All (oldest first)
- Show All (newest first)
ypconstante
You can use a formatter like junit_formatter to have test information without having to use
--trace.sodapopcan
Some companies require you use
--tracefor auditing purposes. I personally think that is stupid but I’ve worked at a place where it was mandated by, I think, the investors? I dunno. Don’t @ me I’m just messenger.garrison
Just to be clear, as the docs mention this flag only disables running tests concurrently with each other. Processes are still preempted and so on.
It sounds like the purpose of this is to debug tests which are somehow interfering with each other in a way that they should not be.
lud
Yes trace is more for debugging the tests. If some company requires --trace for some reason, I would run both versions in CI, so the CI still runs with tests in concurrency that can fail and detect if something is messing with shared state.