Unit Testing단위 테스트

# calculator.py
def add(a, b): return a + b
def divide(a, b):
    if b == 0:
        raise ValueError("0으로 나눌 수 없음")
    return a / b

# test_calculator.py
import pytest
from calculator import add, divide

def test_add_positive():
    assert add(2, 3) == 5

def test_add_negative():
    assert add(-1, -1) == -2

def test_divide_normal():
    assert divide(10, 2) == 5.0

def test_divide_by_zero():
    with pytest.raises(ValueError, match="0으로 나눌 수 없음"):
        divide(10, 0)

# 파라미터화 테스트
@pytest.mark.parametrize("a,b,expected", [
    (1, 2, 3),
    (-1, 1, 0),
    (0, 0, 0),
])
def test_add_parametrize(a, b, expected):
    assert add(a, b) == expected

from unittest.mock import Mock, patch

def test_user_service_get_user():
    mock_repo = Mock()
    mock_repo.find_by_id.return_value = User(1, "Alice")

    service = UserService(mock_repo)
    user = service.get_user(1)

    assert user.name == "Alice"
    mock_repo.find_by_id.assert_called_once_with(1)

# 환경 변수, 외부 함수 패치
with patch('module.requests.get') as mock_get:
    mock_get.return_value.json.return_value = {"id": 1}
    result = fetch_user(1)

def test_something():
    # Arrange: 준비
    user = User(1, "Alice")
    service = UserService(MockRepo())

    # Act: 실행
    result = service.process(user)

    # Assert: 검증
    assert result.status == "processed"