More example states in the unit tests

[sharpchi]

Following on from #878 I was trying to write some tests, but realised the way the testing has been written only allows for one possible event per test. This rather limits exploring all the possible values (including exceptions) that could be tested without resorting to creating a whole new set of data.json, event.json, and statements.json files.

Is there a way we can work in using data providers rather than static files?

[davidpesce]

@sharpchi - This is an interesting and valid thought. I think I'll need to think on this one for a bit. Do you have any suggestions?