Flaky JavaScript tests omnibus ticket

[ivanov]

Our CasperJS tests have a reputation for being at times flaky, primarily due to race conditions and the asynchronous nature of javascript. I am opening this ticket so we can document any time we find Continuous Integration (Travis, etc) tests are failing, so we can track down the race conditions and eliminate them.

Edit: Additionally, I think it won't hurt to put up an extra link to our documentation of how to write, run, and wrap your head around our notebook Javascript tests.

[mpacer]

@michaelpacer, commenting so notifications from this get priority.

[takluyver]

We started using travis_retry on our JS tests on Travis, because we were forever manually restarting failed builds when we suspected a race condition. travis_retry re-runs a command if it fails, up to three times. So be aware that you're probably not seeing most of the test failures.

I'm well aware that this is bad practice too, of course.