Yes Travis CI supports OS X and we used it for a while for Homebrew.
Re:My Experience with Nix on OS X
by Ericson2314 on Monday May 30, 2016 @06:26PM
(#11803574)
The real solution is we need to use our CI, Hydra, to build all PRs.
Now Travis doing this is interesting because last time people looked there was no hosting for OS X that wasn't ridiculously expensive, so we've literally had people donate Mac Minis.
[0]: https://docs.travis-ci.com/user/osx-ci-environment/