Unit testing inathibitisha vitengo vidogo vya kod (functions, methods, classes) kwa kuzitengana — ikiangalia kwamba kila kipande kidogo kinafanya kazi vizuri peke yake. Unit tests ni haraka, zinazolenga, na huunda msingi wa mkakati mzuri wa kupima.
Unit test ni nini
A UNIT test verifies the smallest testable piece (a function/method) in ISOLATION:
→ test ONE thing; give inputs, check the output/behavior
→ ISOLATED from dependencies (database, network, other units) — mock/stub those
→ FAST (no real I/O), focused, deterministic
