Piyé carane nuji aplikasi FastAPI?

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Accepted Answer

FastAPI kalebu aplikasi sing gampang diuji mulai saka **`TestClient`**-ipun (sing dibangun ing Starlette/httpx) lan **sistem dependency injection**-ipun, sing nggawé mocking dependencies dadi gampang. Tes biasane nganggo `pytest` lan `TestClient` kanggo ngirim request menyang app tanpa server sing mlaku.

## Tes endpoint dhasar nganggo TestClient

```python
from fastapi.testclient import TestClient
from main import app

client = TestClient(app)

def test_read_item():
    response = client.get("/items/5")            # send a request to the app in-process
    assert response.status_code == 200
    assert response.json() == {"item_id": 5}

def test_create_item():
    response = client.post("/items", json={"name": "Phone", "price": 999})
    assert response.status_code == 201
    assert response.json()["name"] == "Phone"

def test_validation_error():
    response = client.post("/items", json={"name": "Phone"})   # missing price
    assert response.status_code == 422                          # FastAPI validates automatically
```

`TestClient` ngirim request asli menyang app ing proses (ora perlu server), dadi sampeyan nguji alur lengkap — routing, validasi, serialisasi — lan assert status code lan response JSON.

## Ngganti dependencies (kunci kanggo tes sing bersih)

```python
# override a dependency with a mock/test version — no real database needed
def override_get_db():
    return test_db_session

app.dependency_overrides[get_db] = override_get_db   # swap the real dependency

def test_with_test_db():
    response = client.get("/users")
    # uses the test database via the override
    app.dependency_overrides.clear()                 # reset after
```

`dependency_overrides` FastAPI ngidini sampeyan **ngganti dependency apa wae** (sesi database, auth, layanan eksternal) nganggo test double — fondasi tes cepet lan terisolasi, dadi trivial kanthi desain DI.

## Nuji endpoint sing dilindungi

```python
def test_protected():
    # override the auth dependency to simulate a logged-in user
    app.dependency_overrides[get_current_user] = lambda: fake_user
    response = client.get("/me")
    assert response.status_code == 200
```

## Strategi tes

```text
✓ Use a TEST database (separate, or transactions rolled back per test)
✓ Override dependencies (DB, auth, external APIs) for isolation
✓ Test: status codes, response shapes, validation (422s), auth/permissions, edge cases
✓ For async-specific code, use httpx.AsyncClient / pytest-asyncio
✓ Tools: pytest, factory libraries for test data, coverage.py
```

## Dene iki penting

Pengujian iku penting kanggo aplikasi sing bisa dipercaya, lan FastAPI khusus bisa diuji — mangertèni carane nujiné penting kabaé kanggo kualitas kode lan jalaran framework iki *dirancang* kanggo testability.

**`TestClient`** nggawé gampang kanggo nuji alur request/response lengkap ing proses (ora perlu server), verifikasi routing, validasi, serialisasi, lan response kaya pengalaman klien.

Filtur sing menonjol yaiku **dependency overrides**: amarga FastAPI nganggo dependency injection, sampeyan bisa trivial ngganti dependency apa wae — sesi database, autentikasi, layanan eksternal — nganggo test double liwat `app.dependency_overrides`, ngidini tes cepet lan terisolasi tanpa infrastruktur asli (testability iki yaiku benefit gedhe saka desain DI).

Mangertèni carane nganggo TestClient, ngganti dependencies kanggo isolasi (database tes, auth/layanan sing ditiru), nuji endpoint sing dilindungi, lan nggenteni strategi tes sing bijaksana (status code, bentuk response, validasi, auth, kasus pinggir) yaiku pengetahuan tingkat senior penting kanggo mbangun aplikasi FastAPI sing kokoh.

API sing diuji kanthi apik nyekel regresi lan ngidini refactoring sing percaya diri, lan alat tes FastAPI nggawé tes lengkap dadi lempung, nggawé topik iki relevan lan penting profesional.