Continous integration
Travis CI
Test coverage
Coverage when it comes to testing is a measure of how complete your test suit is. Basically it’s calculated as the percentage of lines of code that are executed during a single run of your test suit.
One practise is to simply not accept pull requests that drop test coverage.
Coveralls
Coveralls.io is a free service (public repos) that integrates with both Travis and GitHub. Test coverage is calculated while running your test suit at Travis. In case of a pull request, Coveralls can also post a comment with the updated coverage. There’s of course also a badge to emblazon your README with.