PART 03 — 単体テスト仕様書
テスト設計の体系と自動化

対象: OrderValidator.validateQuantity(quantity: int)
仕様: 数量は 1以上 9999以下の整数

同値クラス分割:
  有効クラス  : 1 ~ 9999
  無効クラスA : 0以下
  無効クラスB : 10000以上
  無効クラスC : NULL

境界値テストケース:
  ID      | 入力    | 期待
  --------|--------|---------------------
  BV-Q-01 | -1     | ValidationException
  BV-Q-02 | 0      | ValidationException（境界）
  BV-Q-03 | 1      | OK（境界）
  BV-Q-04 | 5000   | OK（代表値）
  BV-Q-05 | 9999   | OK（境界）
  BV-Q-06 | 10000  | ValidationException（境界）
  BV-Q-07 | NULL   | ValidationException

"""
pytest によるテスト仕様書の実装例
pip install pytest
"""
import pytest
from unittest.mock import MagicMock

class BizException(Exception):
    def __init__(self, code):
        self.code = code

class OrderService:
    def __init__(self, order_repo, stock_service):
        self.order_repo = order_repo
        self.stock_service = stock_service

    def confirm_order(self, user_id, product_id, quantity):
        if user_id is None:
            raise ValueError("user_id は必須です")
        available = self.stock_service.check_stock(product_id)
        if available < quantity:
            raise BizException("BIZ_001")
        order = self.order_repo.save(user_id, product_id, quantity)
        return order["order_id"]

class TestOrderServiceConfirmOrder:
    @pytest.fixture
    def service(self):
        repo = MagicMock()
        stock = MagicMock()
        repo.save.return_value = {"order_id": 12345}
        return OrderService(repo, stock), repo, stock

    def test_UT_OS_001_正常系(self, service):
        svc, repo, stock = service
        stock.check_stock.return_value = 10
        result = svc.confirm_order(user_id=1, product_id=100, quantity=1)
        assert result == 12345

    def test_UT_OS_002_在庫不足(self, service):
        svc, repo, stock = service
        stock.check_stock.return_value = 0
        with pytest.raises(BizException) as exc:
            svc.confirm_order(user_id=1, product_id=100, quantity=1)
        assert exc.value.code == "BIZ_001"

    @pytest.mark.parametrize("stock_qty,order_qty,ok", [
        (5, 5, True),   # UT-OS-003: 在庫 = 注文数
        (4, 5, False),  # UT-OS-004: 在庫不足
    ])
    def test_UT_OS_境界値(self, service, stock_qty, order_qty, ok):
        svc, repo, stock = service
        stock.check_stock.return_value = stock_qty
        if ok:
            assert svc.confirm_order(1, 100, order_qty) == 12345
        else:
            with pytest.raises(BizException):
                svc.confirm_order(1, 100, order_qty)

    def test_UT_OS_005_userId_null(self, service):
        svc, _, _ = service
        with pytest.raises(ValueError, match="user_id は必須です"):
            svc.confirm_order(user_id=None, product_id=100, quantity=1)