1

我assertRaises在这样的循环中使用：

for i in ['a', 'b', 'c']: 
    self.assertRaises(ValidationError, my_method, i)

问题是，每当测试失败时，输出如下所示：

  File "/bla/test.py", line 4, in test_assertion
      my_method(i)
AssertionError: ValidationError not raised

如何让它打印出i测试失败时的值？像这样：

  File "/bla/test.py", line 4, in test_assertion
      my_method('b')
AssertionError: ValidationError not raised
4

2 回答 2

2

这是subTests上下文管理器的理想情况。但是，这仅在 python 3 中可用。我认为最好的解决方案是创建自己的subTests. 好处是很容易设置基本的模仿subTests，并且如果subTests曾经向后移植到 python 2，那么它将很容易切换。

import unittest
import sys
from contextlib import contextmanager

class TestCaseWithSubTests(unittest.TestCase):

    @contextmanager
    def subTest(self, **kwargs):
        try:
            yield None
        except:
            exc_class, exc, tb = sys.exc_info()
            kwargs_desc = ", ".join("{}={!r}".format(k, v) for k, v in kwargs.items())
            new_exc = exc_class("with {}: {}".format(kwargs_desc, exc))
            raise exc_class, new_exc, tb.tb_next

class MyTest(TestCaseWithSubTests):

    def test_with_assertion_error(self):
        for i in [0, 1]:
            with self.subTest(i=i), self.assertRaises(ZeroDivisionError):
                1 / i

    def test_with_value_error(self):
        def f(i):
            raise ValueError

        for i in [0, 1]:
            with self.subTest(i=i), self.assertRaises(ZeroDivisionError):
                f(i)


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

产生以下输出：

FE
======================================================================
ERROR: test_with_value_error (__main__.MyTest)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "C:\Users\dunes\py2sub_tests.py", line 30, in test_with_value_error
    f(i)
  File "C:\Python27\lib\contextlib.py", line 35, in __exit__
    self.gen.throw(type, value, traceback)
  File "C:\Users\dunes\py2sub_tests.py", line 30, in test_with_value_error
    f(i)
  File "C:\Users\dunes\py2sub_tests.py", line 26, in f
    raise ValueError
ValueError: with i=0: 

======================================================================
FAIL: test_with_assertion_error (__main__.MyTest)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "C:\Users\dunes\py2sub_tests.py", line 22, in test_with_assertion_error
    1 / i
  File "C:\Python27\lib\contextlib.py", line 35, in __exit__
    self.gen.throw(type, value, traceback)
  File "C:\Users\dunes\py2sub_tests.py", line 22, in test_with_assertion_error
    1 / i
AssertionError: with i=1: ZeroDivisionError not raised

----------------------------------------------------------------------
Ran 2 tests in 0.006s

FAILED (failures=1, errors=1)
于 2015-06-17T10:04:12.920 回答
1

一种解决方案是assertRaises()用作上下文管理器。

with self.assertRaises(ValidationError):
    my_method(i)
    print("Failed when i was",i)

print 语句只有在行成功通过时才会执行my_method()，所以当你的测试失败时它会作为输出出现。有点 hack，但它可以工作（除非my_method()抛出一些不是 a 的错误ValidationError）。

于 2015-06-17T08:52:32.530 回答