@loic good point.  I am making a guess (albeit one with good odds) that portions of the JavaScript code are not executed.

I've noticed in my own code that JavaScript tests often require more mocking than Python code because of the event-driven nature of JS.  So my guess about the lacking nature of the existing tests may not be far from reality, but it's hard to tell for sure without a code coverage tool in place.

I should also note [sinon][] for mocking and a code coverage tool (probably [istanbul][] unless we use [karma][]).

[sinon]: http://sinonjs.org/
[istanbul]: http://gotwarlost.github.io/istanbul/
[karma]: http://karma-runner.github.io/0.12/intro/configuration.html