为什么 python unittest assertRaises 方法不注册抛出的异常？

Question

我有一个类似于的问题，但是解决方案对我没有帮助，因为我只向函数传递了一个参数。

我有以下代码：

def outer():
    def tuple_unpacker( mytuple ):
        try:
            a,b,c = mytuple
            return a+b+c
        except ValueError:
            print('pass tuple with exactly 3 elements')
        except TypeError:
            print('pass only integers in tuple')

    return tuple_unpacker

我使用 python unittest 模块进行测试。但是，即使出现我的异常，断言也会失败。

class TestInner(unittest.TestCase):
    def test_tuple_unpacker(self):
        func = outer()
        self.assertRaises(TypeError, func, (1,'a',1))
        self.assertRaises(ValueError, func, (1,1,1,1))

当我运行这个的时候，traceback是：

pass only integers in tuple
F
======================================================================
FAIL: test_tuple_unpacker (__main__.TestInner)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/Users/malte/TDDE23_git/lab5/test_test.py", line 21, in test_tuple_unpacker
    self.assertRaises(TypeError, func, (1,'a',1))
AssertionError: TypeError not raised by tuple_unpacker

----------------------------------------------------------------------
Ran 1 test in 0.000s

如您所见，它打印了 pass only integers in tuple 因此抛出了异常。

如果我切换位置，问题是相同的，所以首先测试 ValueError 并失败。

奇怪的是，如果我将断言更改为：

class TestInner(unittest.TestCase):

    def test_tuple_unpacker(self):
        func = outer()
        self.assertRaises(TypeError, func((1,'a',1)))
        self.assertRaises(ValueError, func((1,1,1,1)))

它适用于 TypeError，但不适用于 ValueError。

这是回溯：

pass only integers in tuple
pass tuple with exactly 3 elements
E
======================================================================
ERROR: test_tuple_unpacker (__main__.TestInner)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/Users/malte/TDDE23_git/lab5/test_test.py", line 22, in test_tuple_unpacker
    self.assertRaises(ValueError, func((1,1,1,1)))
  File "/usr/local/Cellar/python@3.9/3.9.7/Frameworks/Python.framework/Versions/3.9/lib/python3.9/unittest/case.py", line 731, in assertRaises
    return context.handle('assertRaises', args, kwargs)
  File "/usr/local/Cellar/python@3.9/3.9.7/Frameworks/Python.framework/Versions/3.9/lib/python3.9/unittest/case.py", line 201, in handle
    callable_obj(*args, **kwargs)
TypeError: 'NoneType' object is not callable

----------------------------------------------------------------------
Ran 1 test in 0.001s

FAILED (errors=1)

感谢所有指导。

Answer 1

tuple_unpacker 打印然后抑制 TypeError 和 ValueError 异常。您的测试会检查这些异常，但由于未重新引发异常，因此测试失败。功能或测试有错误，需要更改。

为什么 python unittest assertRaises 方法不注册抛出的异常？

Why does python unittest assertRaises method not register exceptions that are thrown?

python

unit-testing

python-unittest

assert

valueerror