unittest instance objects exist for the lifetime of the py.test run

[d-b-w]

unittest.TestCase instance objects are never cleaned up - the py.test unittest module retains references to them for the whole of the py.test run. In my case, this can cause problems because the unittest.TestCase instance objects can have large objects associated with them. I believe that people writing unittest-based tests expect that their objects will be cleaned up after test execution.

I've seen this on Linux/Darwin/Windows
pytest==2.8.7
pytest-cov==2.2.1
pytest-faulthandler==1.3.0
pytest-xdist==1.14

Example:

Given this test:

import unittest

class Demo(unittest.TestCase):
    def setUp(self):
        self.large_object = list(range(10**6))
    def testDemo(self):
        assert len(self.large_object) == 10**6

The memory allocated for larg_object will be in use for the whole py.test run, even after it is done with this test.

[d-b-w]

I believe that it would be sufficient to set the TestCaseFunction instance's _testcase and _obj attributes to None after all cleanup is complete.

[d-b-w]

See also the report here: http://stackoverflow.com/questions/20900380/py-test-excessive-memory-usage-with-large-number-of-tests

[RonnyPfannschmidt]

Feel like trying to do a PR?

[d-b-w]

Yeah, I'd like to. I have some testing to do with my idea, though - it seems to cause some problems with our test set.