Piye carane nambah tes menyang kode warisan?

Question

IT Interview Practice · Accepted Answer

**Kode warisan** (asring dudu tes, kode sing angel dirubah) iku tantangan kanggo tes — bisa uga gadhean ketergantungan lan tanpa tes. Nambah tes kanthi aman melu teknik kaya **characterization tests**, **seams** kanggo ngputus ketergantungan, lan perbaikan bertahap, nggawe owah-owahan luwih aman.

## Tantangan kode warisan

```text
Legacy code is often: untested, tightly coupled, hard to understand, risky to change:
  → no tests → changing it is dangerous (you can't tell if you broke something)
  → hard to test → dependencies are tangled (can't isolate units); not designed for testing
→ a chicken-and-egg problem: to change safely you need tests, but it's hard to test.
```

## Characterization tests (tetepkan tingkah laku saiki)

```text
CHARACTERIZATION (golden master) tests → capture the code's CURRENT behavior as-is
  (even if you don't fully understand it / it has bugs):
  → write tests asserting what it ACTUALLY does now → a SAFETY NET
  → then you can refactor/change with confidence that behavior is preserved
→ Don't assert what it SHOULD do — assert what it DOES, to protect against regressions.
```

## Ngputus ketergantungan (seams)

```text
To isolate hard-to-test code, find/create SEAMS (places to substitute dependencies):
  → extract dependencies behind interfaces; inject them; use the smallest safe refactors
    to make code testable (Michael Feathers' techniques)
  → carefully break dependencies so you can get the code under test, then test, then refactor
```

## Pendekatan bertahap

```text
✓ Add tests AROUND code BEFORE changing it (a safety net for the change)
✓ Focus on areas you're CHANGING / high-risk / high-value (not the whole codebase at once)
✓ Improve incrementally — leave code a bit better each time (the "boy scout rule")
✓ Use characterization tests to capture behavior, then refactor toward testability
```

## Kenapa iku penting

Ngerti carane nambah tes menyang kode warisan iku ilmu tingkat senior sing berharga amarga **umume karya nyata melu kode sing wis ana, asring dudu tes**, lan nambah kanthi aman iku tantangan umum lan penting, dadi relevan kanthi praktis.

Kode warisan (dudu tes, rapet banget, angel dirubah) ngandhut masalah **chicken-and-egg** nyata: supaya owah kanthi aman butuh tes, nanging angel ngetest (ketergantungan ruwet, ora dirancang kanggo tes) — lan owah kode sing dudu tes iku mbahayani amarga ora bisa waca apa sing pecah.

Ngerti teknik kanggo tanggulangi iki iku ilmu praktis berharga. **Characterization tests** (nabol tingkah laku kode *saiki* kaya-kaya, assertion apa sing bener-bener ditindakake tinimbang apa sing kudu — sanajan ora dong penuh) nyedhiyakake **safety net** sing nggawe refactor lan owah kanthi yakin tingkah laku sing wis ana iku tetep — teknik utama kanggo kerja karo kode sing ora dong penuh.

Ngerti **ngputus ketergantungan via seams** (nemokake utawa nggawe panggonan kanggo ganti ketergantungan, nggunakake refactor sing minimal aman kanggo nggawe kode ruwet bisa dites — teknik saking karya Michael Feathers babagan kode warisan) iku penting kanggo ngebut kode sing angel dites dadi kena tes.

Ngerti **pendekatan bertahap** — nambah tes sakuburing kode sadurunge owah (safety net kanggo owah), fokus ing wilayah sing diowah utawa risiko-duwur/nilai-duwur (ora kabeh codebase sakndhap), lan nambah bertahap (boy scout rule) — ngrembug cara pragmatis, realis kanggo nambah sistem warisan sajrone wektu.

Amarga umume pengembangan nyata melu kode warisan sing wis ana, asring dudu tes, sing kudu owah kanthi aman (situasi umum, tantangan), lan amarga ngerti teknik (characterization tests kanggo safety net, seams kanggo ngputus ketergantungan, perbaikan bertahap) nggawe iki bisa ditindakake, ngerti carane nambah tes menyang kode warisan iku ilmu tingkat senior sing berharga — relevan praktis kanggo kasunyatan umum kerja karo kode warisan dudu tes, ngrembug pengalaman lan teknik sing ditbutuhake kanggo nambah sistem warisan kanthi aman, kompetensi penting kanggo insinyur senior sing asring kudu nggawe kode dudu tes luwih aman dirubah.

Tantangan kode warisan

Characterization tests (tetepkan tingkah laku saiki)

Ngputus ketergantungan (seams)

Pendekatan bertahap

Kenapa iku penting

Pitakon sing gegandhengan