pytest: raises regexp

Originally reported by: György Kiss (BitBucket: kissgyorgy, GitHub: kissgyorgy)

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I used assertRaisesRegexp in unittest and I miss it from pytest. As I don’t want to use unittest anymore 😄 I wrote a context manager:

#!python

import pytest
import py

class raises_regexp(object):
    def __init__(self, exception, message):
        self.exception = exception
        self.message = message
        self.excinfo = None

    def __enter__(self):
        self.excinfo = object.__new__(py.code.ExceptionInfo)
        return self.excinfo

    def __exit__(self, exc_type, exc_val, exc_tb):
        __tracebackhide__ = True
        if exc_type is None:
            pytest.fail('DID NOT RAISE %s' % self.exception)

        self.excinfo.__init__((exc_type, exc_val, exc_tb))

        if not issubclass(self.excinfo.type, self.exception):
            pytest.fail('%s RAISED instead of %s' % (exc_type, self.exception))

        if self.message not in str(exc_val):
            pytest.fail('message "%s" not found in "%s"' % (self.message, str(exc_val)))

        return True

Usage:

#!python

def test_some_exception_thrown():
    with raises_regexp(ExpectedException, "message contained"):
       # code to test

I think others could benefit from something like this and would be nice to have it in pytest!

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• Bitbucket: https://bitbucket.org/pytest-dev/pytest/issue/372