Visa vya kando ni pembejeo na hali yasiyokawaida au za mipaka mahali ambapo hitilafu mara nyingi hujificha — pembejeo tupu, mipaka, nulls, thamani kubwa, hitilafu. Ujaribu wenye ufanisi unazidi "njia yenye furaha" ili kuishe, kwa kuwa visa vya kando ni chanzo cha kawaida cha hitilafu halisi.
Kwa nini visa vya kando ni muhimu
The HAPPY PATH (normal, expected inputs) usually works. BUGS hide in EDGE CASES:
→ unusual inputs, boundaries, error conditions, unexpected states
→ testing only the happy path misses where defects actually occur
→ Thorough testing covers edge cases — that's where it adds the most value.
Kategori za kawaida za visa vya kando
EMPTY / NULL → empty string/list/collection, null/undefined, missing values
BOUNDARIES → min/max values, 0, -1, off-by-one (first/last element, limits)
LARGE / extreme → very large inputs, long strings, huge numbers, overflow
INVALID → wrong types, malformed data, out-of-range, special characters
ERROR conditions → network failures, exceptions, timeouts, unavailable dependencies
STATE → empty/initial state, concurrent access, unexpected sequences of actions
SPECIAL values → negative numbers, zero, duplicates, unicode/emoji, very small/large
