How to create a custom output formatter?

[meleu]

I see that currently the available formatters are pretty, junit, tap, and tap13. I also see that the help message mentions /<absolute path to formatter>. Then my question is:

Is there any documentation or example code showing how to write a formatter?

---

my motivation

I want a minimalist output, like we see in many other languages' testing frameworks. Where the passing tests are just . dots and only the failing tests print actual text.

If someone already know how to achieve this, that's even better! 🙂

Example taken from minitest's README:

% ruby -Ilib:test test/minitest/test_minitest_test.rb
Run options: --seed 37685

# Running:

...................................................................... (etc)

Finished in 0.107130s, 1446.8403 runs/s, 2959.0217 assertions/s.

155 runs, 317 assertions, 0 failures, 0 errors, 0 skips