Apa iku test coverage?

Question

Accepted Answer

**Test coverage** ngukur sapirang akeh kode sing **dijalanke dening tes** — biasane minangka persentase (contone 80% coverage). Iki minangka metrik sing migunani kanggo nemokake kode sing ora ditesti, nanging penting kanggo ngerti limitations-ne: coverage sing dhuwur ora njamin tes sing apik.

## Apa sing diukur coverage

```text
TEST COVERAGE = the % of code exercised by the test suite:
  LINE coverage → % of code lines executed by tests
  BRANCH coverage → % of branches (if/else paths) taken
  FUNCTION coverage → % of functions called
  STATEMENT coverage → % of statements executed
→ Coverage tools instrument the code and report what tests do/don't exercise.
```

## Mengapa coverage itu gunani

```text
✓ FINDS UNTESTED code — low coverage areas reveal what lacks tests (a gap finder)
✓ A measurable quality signal; track it over time; many teams set a target (e.g. ≥80%)
✓ Highlights branches/paths/error cases that tests miss
```

## Limitations-ne (penting!)

```text
⚠️ HIGH COVERAGE ≠ GOOD TESTS:
  → coverage shows code was EXECUTED, NOT that behavior was correctly VERIFIED
  → you can execute code with NO meaningful assertions → 100% coverage, tests verify nothing
  → 100% coverage can still miss bugs (untested input combinations, logic errors)
⚠️ Chasing a coverage NUMBER → writing low-value tests just to hit the target
→ Coverage is a USEFUL guide (find gaps), NOT a guarantee of quality. Use it wisely;
  focus on testing important behavior well, not just hitting a percentage.
```

## Mengapa iku penting

Ngerti test coverage — kalebu limitations-ne — iku berharga jalaran iku minangka **metrik sing asring digunakake** sing gunani yen dimangerteni kanthi bener nanging bisa nyasakake yen disalahgunakake, dadi iku pengetahuan praktis sing penting.

Coverage ngukur **sapirang akeh kode sing dijalanke dening tes** (minangka persentase, liwat line, branch, function, utawa statement coverage), lan ngerti iki gunani jalaran iku **nemokake kode sing ora ditesti** (nembongake kekosongan ing ngendi tes kurang — cara sing berharga kanggo identifikasi apa sing perlu ditesti), menehi sinyal kualitas sing bisa diukur tim bisa dilacak, lan ngebongkar branch lan error cases sing kecilik.

Lawak tim nggunakake coverage minangka metrik kualitas kanthi target.

Nanging, ngerti **limitations iki sangat penting**: **coverage sing dhuwur ora padha karo tes sing apik** — coverage katon kode wis *dijalanke*, ora yen perilaku-ne wis bener *diverifikasi*, mula sampeyan bisa duwe coverage sing dhuwur (malah 100%) kanthi tes sing tanpa makna (njalanke kode tanpa assertion sing bener ora neverifikasi apa-apa), lan coverage lengkap isih bisa kecilik bugs (kombinasi input sing ora ditesti, kesalahan logika).

Bahaya **mengejar angka coverage** (nulis tes sing nilai durung tinggi mung kanggo tekan target) minangka anti-pattern sing nyata.

Ngerti yen **coverage iku guide sing gunani kanggo nemokake kekosongan, ora jaminan kualitas** — lan fokus kuwi kudu ing testing perilaku penting kanthi apik tinimbang tekan persentase — nggambarke penghakiman mateng sing ngindhari kesalahan umum nganggep coverage minangka tujuan tinimbang piranti.

Sakdening coverage minangka metrik sing asring digunakake sing bener-bener gunani (nemokake kode sing ora ditesti) nanging asring ora dimangerteni kanthi salah lan disalahgunakake (dianggap minangka jaminan kualitas utawa target kanggo ditipu), lan jalaran ngerti bote nilai lan limitations penting iki ngaksesaken nggunakake kanthi wicaksana, ngerti test coverage minangka pengetahuan berharga, praktis sing relevan — metrik gunani kanggo dimangerteni kanthi bener, ing ngendi nganggep limitations-ne (coverage ≠ kualitas) iku padha pentinge karo metrik dhewe, nggambarke penilaian testing sing sinom.