in Travis you can run your test suite on many different Elixir versions.
This is how I found out that I am now, while upgrading dependencies, often no longer able to support elixir v1.2 (but I personally think that that version is now old enough to leave behind).
Currently, my plain test .travis.yml
configuration looks like this:
language: elixir
elixir:
- 1.3.2
- 1.4.5
- 1.5.3
- 1.6.6
- 1.7.4
- 1.8.0