Self-testing code exists when you can run a series of automated tests against the code base and be confident that, should the tests pass, your code is free of any substantial defects. Self-testing code is a key part of Continuous Integration, and it's said that you aren't doing continuous integration unless you have self-testing code. As a pillar of Continuous Integration, it is also a necessary part of Continuous Delivery.
In Skai, we should continue utilizing our automation infrastructures (JUnit, Karate, Cucumber and more) to maintain a high testing coverage.