Concourse explicitly wants to not know anything about the outputs of your jobs. Most of the other ci products will have _some_ method (integration with common test runners, markers in output) to figure out how many tests you've run and display them as a collapsible outline, or something similar.

Because the ci system is aware of your tests, and perhaps a filename/test description, it can keep stats on them over time.

This is an ancient version of teamcity [0], but it shows how it knows how many tests were run, how many passed, and that there's one "new" failure in this run vs previous runs.

This lets it tell you which tests are slow, which are flaky, all sorts of history of those wrt to state of the associated repo, etc.

Not having these sorts of things once you have them is like flying blind.

[0] https://i.imgur.com/ywB7u11.png