"""简单计算器测试"""
import unittest


def add(a, b):
    return a + b


def subtract(a, b):
    return a - b


def multiply(a, b):
    return a * b


def divide(a, b):
    if b == 0:
        raise ValueError("除数不能为零")
    return a / b


class TestCalculator(unittest.TestCase):

    def test_add(self):
        self.assertEqual(add(1, 2), 3)
        self.assertEqual(add(-1, 1), 0)

    def test_subtract(self):
        self.assertEqual(subtract(5, 3), 2)

    def test_multiply(self):
        self.assertEqual(multiply(3, 4), 12)
        self.assertEqual(multiply(0, 100), 0)

    def test_divide(self):
        self.assertEqual(divide(10, 2), 5)
        with self.assertRaises(ValueError):
            divide(1, 0)


if __name__ == "__main__":
    unittest.main()