Add fake data generation & testing

[rbuchberger]

Currently I'm manually using a known sample for testing. Problem is it's huge and correct or incorrect numbers are hard to spot.

• Add ability to generate fake data using simple, round numbers, where correct answers are also obvious
• Add tests to verify chunker.
• Add simple UI tests - don't test EVERY detail, we don't want to slow down development, but make sure the important parts of the happy path work.