[lisivka]

I saw so many bugs, so I switched from "code is working" by default to "code is broken" by default unless it proven that code is working correctly at target environment with required constraints.

Moreover, test cases are saving development time massively, so why waste time for manual tests and debugging sessions, when I can use computer to do that instead of me? When practiced regularly, test cases are written in tens of seconds. For example, if I will work on a calculator, I will write something like assertEquals(calculate("2+2"), 4, "Result of arithmetic addition is wrong."); Then I will work on calculator until this test will pass. Only then I may start to write unit tests. It's easy and fast, so why not?