Add unit tests for reports

[FranjoMindek]

Reports are one of the most important features of the wasp-bot.
Currently, it's very hard to refactor logic which works with reports without being sure that end output isn't affected.
We should add unit tests for each of the reports so we can be faster in future.

[Martinsos]

What would you test, actual images generated? Or aha, you could test the final config generated before it is sent to the service that generates the image out of it.

[FranjoMindek]

Oh a mistake, ment to refer to report rather than chart, I'll fix it.

Basically test all report data, which currently is: text, csv, and image.
To generate image we send "svg-like text", we can test that.