Refactor code structure for improved readability and maintainability

tests/test_api_contract.py

@@ -0,0 +1,58 @@
+import uuid
+
+from fastapi import FastAPI
+from fastapi.testclient import TestClient
+
+from app.api import router
+
+
+def make_client() -> TestClient:
+    app = FastAPI()
+    app.include_router(router)
+    return TestClient(app)
+
+
+def test_get_payment_requires_api_key() -> None:
+    with make_client() as client:
+        response = client.get(f"/api/v1/payments/{uuid.uuid4()}")
+
+    assert response.status_code == 401
+    assert response.json() == {"detail": "Invalid or missing API key"}
+
+
+def test_create_payment_requires_idempotency_key() -> None:
+    with make_client() as client:
+        response = client.post(
+            "/api/v1/payments",
+            headers={"X-API-Key": "change-me"},
+            json={
+                "amount": "100.00",
+                "currency": "RUB",
+                "description": "Test payment",
+                "metadata": {},
+                "webhook_url": "https://example.com/webhook",
+            },
+        )
+
+    assert response.status_code == 422
+    assert response.json()["detail"][0]["loc"] == ["header", "Idempotency-Key"]
+
+
+def test_create_payment_rejects_unsupported_currency() -> None:
+    with make_client() as client:
+        response = client.post(
+            "/api/v1/payments",
+            headers={
+                "X-API-Key": "change-me",
+                "Idempotency-Key": "test-key",
+            },
+            json={
+                "amount": "100.00",
+                "currency": "GBP",
+                "description": "Test payment",
+                "metadata": {},
+                "webhook_url": "https://example.com/webhook",
+            },
+        )
+
+    assert response.status_code == 422

tests/test_retry.py

@@ -0,0 +1,53 @@
+import pytest
+
+from app.processing import retry_async
+
+
+@pytest.mark.asyncio
+async def test_retry_uses_exponential_delay_and_returns_success() -> None:
+    calls = 0
+    delays: list[float] = []
+
+    async def operation() -> str:
+        nonlocal calls
+        calls += 1
+        if calls < 3:
+            raise RuntimeError("temporary failure")
+        return "processed"
+
+    async def record_sleep(delay: float) -> None:
+        delays.append(delay)
+
+    result = await retry_async(
+        operation,
+        attempts=3,
+        base_delay=1,
+        sleep=record_sleep,
+    )
+
+    assert result == "processed"
+    assert calls == 3
+    assert delays == [1, 2]
+
+
+@pytest.mark.asyncio
+async def test_retry_raises_last_error_after_three_attempts() -> None:
+    calls = 0
+
+    async def operation() -> None:
+        nonlocal calls
+        calls += 1
+        raise RuntimeError(f"failure {calls}")
+
+    async def no_sleep(_: float) -> None:
+        pass
+
+    with pytest.raises(RuntimeError, match="failure 3"):
+        await retry_async(
+            operation,
+            attempts=3,
+            base_delay=1,
+            sleep=no_sleep,
+        )
+
+    assert calls == 3