Asserting repeated warning does not work in Python 2.7 #2917
Description
Running the following test code with Python 2.7 will fail because for some reason the warning is not emitted a second time:
import warnings
import pytest
def warn():
warnings.warn(UserWarning("test"))
def test_warning():
warn()
with pytest.warns(UserWarning):
warn()The output:
============================= test session starts ==============================
platform linux2 -- Python 2.7.13, pytest-3.2.3, py-1.4.34, pluggy-0.4.0
rootdir: /home/jgosmann, inifile:
collected 1 item
test2.py F
=================================== FAILURES ===================================
_________________________________ test_warning _________________________________
def test_warning():
warn()
with pytest.warns(UserWarning):
> warn()
E Failed: DID NOT WARN. No warnings of type (<type 'exceptions.UserWarning'>,) was emitted. The list of emitted warnings is: [].
test2.py:13: Failed
=============================== warnings summary ===============================
test2.py::test_warning
/home/jgosmann/test2.py:7: UserWarning: test
warnings.warn(UserWarning("test"))
-- Docs: http://doc.pytest.org/en/latest/warnings.html
===================== 1 failed, 1 warnings in 0.01 seconds =====================Running with Python 3.6.1 succeeds:
============================= test session starts ==============================
platform linux -- Python 3.6.1, pytest-3.2.3, py-1.4.34, pluggy-0.4.0
rootdir: /home/jgosmann, inifile:
collected 1 item
test2.py .
=============================== warnings summary ===============================
test2.py::test_warning
/home/jgosmann/test2.py:7: UserWarning: test
warnings.warn(UserWarning("test"))
-- Docs: http://doc.pytest.org/en/latest/warnings.html
===================== 1 passed, 1 warnings in 0.00 seconds =====================Note that this also occurs across different tests, e.g. when parametrizing:
@pytest.mark.parametrize('i', range(2))
def test_warning(i):
if i % 2 == 0:
warn()
else:
with pytest.warns(UserWarning):
warn()When running tests with pytest-xdist in non-deterministic order this can cause random test failures with Python 2.7.