Now Travis can run the screenshotter in verification mode. The files in the
repository will be seen as the expected outcome, and if the actual result
differs from that, it might be attempted four more times before the test
case is actually deemed failed. A timeout between page load and screenshot
should allow any possible font issues to settle down.
Thanks to the docker service provided by Travis CI, we should be able to
download and use the Selenium docker images in order to run our
screenshotter and check whether all the screenshots match the images from
the repository.
This tests against Node 0.10 (latest stable) and 0.11 (latest dev).
Test Plan: Crossed fingers. In theory we'll see this at https://travis-ci.org/Khan/KaTeX as soon as I push it.
Auditors: emily
