Cover everything with unit-tests

[Igmat]

DISCLAIMER: we have e2e tests which are enough to say that tool is working (likely correct), so don't be afraid.

It's weird that test framework isn't covered by unit-test, but for now it's only place to test #65, #69, #14, #60, #67, #57, #55, #59 in real project.

So after closing all mentioned issues, all code of this project will be covered by tests ASAP and further development process will follow TDD-like approach.