050-testing

🧪 TESTING — TRADING TERMINAL

FILOSOFÍA: CÓDIGO SIN TEST = CÓDIGO ROTO

En una terminal de trading, un bug puede significar pérdida de dinero. Cada función de lógica de negocio DEBE tener al menos un test.

🐍 TESTS BACKEND (Python/Pytest)

Estructura de tests:

tests/
├── unit/                    ← Tests de funciones individuales (rápidos)
│   ├── test_risk_service.py
│   ├── test_order_service.py
│   └── test_calculators.py
├── integration/             ← Tests de flujos completos (más lentos)
│   ├── test_order_flow.py
│   └── test_auth_flow.py
├── fixtures/                ← Datos de prueba compartidos
│   └── trading_fixtures.py
└── conftest.py              ← Configuración global de pytest

Template de test unitario:

# tests/unit/test_risk_service.py
import pytest
from decimal import Decimal
from unittest.mock import AsyncMock, patch

from app.services.risk_service import RiskService
from app.schemas.order_schema import OrderCreate
from app.core.exceptions import RiskViolationError, InsufficientFundsError

class TestRiskService:
    """Tests del servicio de gestión de riesgo."""

    @pytest.fixture
    def risk_service(self):
        return RiskService()

    @pytest.fixture
    def mock_portfolio(self):
        return {
            "available_usd": Decimal("5000"),
            "total_value": Decimal("10000")
        }

    # ========== HAPPY PATH ==========

    async def test_valid_order_passes_validation(self, risk_service, mock_portfolio):
        """Orden válida dentro de límites debe pasar."""
        order = OrderCreate(
            symbol="BTCUSDT",
            side="BUY",
            order_type="MARKET",
            quantity=Decimal("0.01")
        )
        current_price = Decimal("40000")

        # No debe lanzar excepción
        await risk_service.validate_order(order, mock_portfolio, current_price)

    # ========== CASOS BORDE ==========

    async def test_order_exceeding_max_size_raises_error(self, risk_service, mock_portfolio):
        """Orden > $10,000 debe ser rechazada."""
        order = OrderCreate(
            symbol="BTCUSDT",
            side="BUY",
            order_type="MARKET",
            quantity=Decimal("1.0")  # 1 BTC a $40k = $40,000
        )

        with pytest.raises(RiskViolationError) as exc_info:
            await risk_service.validate_order(order, mock_portfolio, Decimal("40000"))

        assert "excede límite" in str(exc_info.value)

    async def test_insufficient_funds_raises_error(self, risk_service):
        """Orden sin fondos suficientes debe ser rechazada."""
        poor_portfolio = {
            "available_usd": Decimal("100"),
            "total_value": Decimal("100")
        }
        order = OrderCreate(
            symbol="BTCUSDT",
            side="BUY",
            order_type="MARKET",
            quantity=Decimal("0.1")  # $4,000
        )

        with pytest.raises(InsufficientFundsError):
            await risk_service.validate_order(order, poor_portfolio, Decimal("40000"))

    async def test_negative_quantity_raises_error(self, risk_service, mock_portfolio):
        """Cantidad negativa debe ser rechazada por Pydantic."""
        with pytest.raises(ValueError):
            OrderCreate(
                symbol="BTCUSDT",
                side="BUY",
                order_type="MARKET",
                quantity=Decimal("-1.0")
            )