Missing unit tests

[d047491]

There should be unit test in order to make sure, that future implementations, refactorings or performance optimizations don't break anything.

[mawerty]

Who needs tests, if the code returns the wrong answer too often, it means that it is working correctly but it just got very unlucky with the 5% of tests

[DavidJS01]

if the code works 95% of the time I don't see the need for tests