Skip expected failures

xfail, python, test, testing, unittest
pip install xfail==1.1.2




XFail provides a decorator function xfail to skip expected exceptions. Similar to unittest.skipIf, but xfail can specify which exception should be skipped, and raise if the decorated function is unexpectedly passed (only if strict is True).


Supported python versions are: 2.7, 3.4, 3.5, 3.6

Can be installed from PyPI by pip:

pip install xfail


xfail decorator

xfail accepts two arguments, exceptions and strict.

The first argument (exceptions) should be an Exception class to skip (Ex. Exception, AssertionError, and so on). If you want to skip multiple exceptions, use tuple of them, for example, @xfail((AssertionError, ValueError)).

The second argument strict should be a boolean. If strict is False (by default) and passed unexpectedly, raise unittest.SkipTest exception, which will mark the test is skipped. This case is very similar to the function is decorated by uniteest.skip function and the test will be counted as skipped.

If it is True and the decorated function did not raise (any of) the expected exception(s), XPassFailure exception would be raised. In this case, the test will be counted as fail.
from xfail import xfail

def get(l, index):
    return l[index]

l = [1, 2, 3]
get(4)  # no error

Also supports multiple exceptions:

@xfail((IndexError, ValueError))
def a():
    '''This function passes IndexError and ValueError

In test script, similar to unittest.TestCase.assertRaises:

from unittest import TestCase
from xfail import xfail

class MyTest(TestCase):
    def test_1(self):
        def should_raise_error():
            assert False
        a()  # test passes

    def test_2(self):
        @xfail(AssertionError, strict=True)
        def should_raise_error():
            assert True
        a()  # test failes, since this function should raise AssertionError

    # Can be used for test function
    @xfail(AssertionError, strict=True)
    def test_3(self)
        assert False

    # This test will fail
    @xfail(AssertionError, strict=True)
    def test_3(self)
        assert True

For more exapmles, see test_xfail.py.