Added test timeout and self-terminating tests

Included in this pull request:

- 2 second timeout for test suite
- Added self-terminating test

In an attempt to get [substack/testling][testling] to run, I am inspecting the modules it depends on.

As it turns out, I did not have `xvfb` installed on my machine which caused me to miss the assertions ever get made. After installing `xvfb`, I verified the assertions were running but the process still wasn't terminating. As a result, I added some self-terminating logic. As a gesture of good faith, I added in a test timeout for future brave lost souls.

[testling]: https://github.com/substack/testling/