tornado.testing can swallow exceptions

[dwt]

I've just lost a whole day until I figured out why my test suite suddenly exploded completely.

Here's what happened:

• A test of mine exercises colanders validation logic to see if correctly rejecting invalid input
• Suddenly my whole test suite exploded
• It takes hours of debugging until I learn that the AsyncTestCase somehow swallows exceptions raised during logging an exception that is thrown in a test.
• To be exact, colander throws an exception that throws an exception when you str() it
• tornado.testing swallows that exception, starts the next test and lets me stay to wonder why suddenly test isolation is broken
• which happens because teardown isn't run.

Here's a reduction that nicely demonstrates the problem for me.

import unittest
import logging
from tornado.testing import AsyncTestCase

class Test(AsyncTestCase):

    def test(self):
        class FaultingException(Exception):
            def __str__(self):
                raise TypeError()
        # comment the next line to see it dying normaly
        logging.warn('baz to logging.warn')
        raise FaultingException()

# Run with $ nosetests test.py
# watch it die without reporting the exception

[dwt]

Corresponding issue in nose tests: https://github.com/nose-devs/nose/issues/443

[bdarnell]

This looks like a nose problem (at least in this reduction). I took your test case and added a call to unittest.main() at the end, and when run directly it fails as expected.

[dwt]

This is correct, it fails badly in the interaction with nose, as nose has a wrapper around the unittest plugins that catches the error too, but is disabled by tornado.testing.

That is why I have reported the Issue on both sides.