Python单元测试失败: should raise value error but not

Question

这是我尝试学习单元测试的代码。创建一个 Student 类以进行测试。测试无效的测试用例不断失败。

FAIL: test_invalid (__main__.TestStudent)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "mystudent.py", line 46, in test_invalid
    s1.get_grade()
AssertionError: ValueError not raised

以上是运行结果。

有人可以帮我弄清楚为什么我会出现此故障，而我认为我已经在那里放置了正确的“引发错误”代码......

import unittest

class Student(object):
def __init__(self, name, score):
    self.name = name
    self.score = score


def get_grade(self):
    try:
        if self.score >= 60 and self.score < 80:
            return 'B'
        if self.score >= 80 and self.score <= 100:
            return 'A'
        if self.score >= 0 and self.score <60:
            return 'C'
        if self.score < 0 or self.score > 100:
            raise ValueError('Invalid score value')
    except Exception as e:
        print('Value error!')


class TestStudent(unittest.TestCase):


def test_invalid(self):
    s1 = Student('Bob', -1)
    s2 = Student('Bat', 101)
    with self.assertRaises(ValueError):
        s1.get_grade()
    with self.assertRaises(ValueError):
        s2.get_grade()


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

谢谢

Answer 1

您正在函数内捕获ValueError。您需要删除函数中的 try/ except block ，或者在执行您想要的操作后重新raise它:

def get_grade(self):
    try:
        if self.score >= 60 and self.score < 80:
            return 'B'
        if self.score >= 80 and self.score <= 100:
            return 'A'
        if self.score >= 0 and self.score <60:
            return 'C'
        if self.score < 0 or self.score > 100:
            raise ValueError('Invalid score value')
    except Exception as e:
        print('Value error!') 
        raise  # Passes the exception up