Figure out how to test the `index.js`

I'm not really sure what the conventions are in the JS world for this. In Python you would put all executing code inside functions and then have something like:

```python
if __name__ == "__main__":
main()
```
There are some interesting ideas here: https://stackoverflow.com/questions/27634634/nodejs-how-to-test-index-js-without-module-exports
I'm not sure I entirely like them though. This will probably need more investigation to figure out a good pattern.