assertRaises 无法捕捉错误

Question

我有一个脚本

import unittest,itertools,random

##testclass
class Testcomb(unittest.TestCase):

     def test_input(self):
        self.assertRaises(TypeError,calculate_combinations,dict(comb1), 5)

def calculate_combinations(combin,target):
    counter = 0
    for L in range(0, len(combin)+1):
      for subset in itertools.combinations(combin, L):
        if sum(subset) == target: counter= counter+1
    return counter

comb1=[1,2,3,4]


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

但是这个 self.assertRaises(TypeError,calculate_combinations,dict(comb1), 5) 代码没有捕捉到异常，导致我收到了这个错误：

E..
======================================================================
ERROR: test_input (__main__.Testcomb)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "total_combination.py", line 25, in test_input
    self.assertRaises(TypeError,calculate_combinations,dict(comb1), 5)
TypeError: cannot convert dictionary update sequence element #0 to a sequence

----------------------------------------------------------------------
Ran 3 tests in 0.000s

FAILED (errors=1)

有人能帮忙吗？

Answer 1

导致你的测试失败的错误是由 dict(comb1) 这一部分引起的。

>>> comb1=[1,2,3,4]
>>> dict(comb1)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: cannot convert dictionary update sequence element #0 to a sequence

相反，只有当可调用的东西（在你的例子中是 calculate_combinations）触发了它时，assertRaises 才会返回 True。

希望这对你有帮助！