Clean up unittest TestCase objects after tests are complete (#1649).

[d-b-w]

Fix #1649

Users of unittest style TestCases will create expensive objects
in setUp. We should clean up TestCase instances that are lying
around so that they don't fill up memory.

Here's a quick checklist that should be present in PRs:

• Target: for bug or doc fixes, target master; for new features, target features; (master)
• Make sure to include one or more tests for your change; (test_teardown_issue1649(), fails before and passes after)
• Add yourself to AUTHORS; (as Daniel Wandschneider)
• Add a new entry to CHANGELOG.rst (Added first line of this description)

[coveralls]

Coverage increased (+0.002%) to 92.798% when pulling e46e653 on d-b-w:clean-up-unittest-issue1649 into 07af307 on pytest-dev:master.

[The-Compiler]

Looking at http://stackoverflow.com/questions/40478600/mem-leak-in-pyqt-test-with-pytest should we do the same with other test classes too?

[d-b-w]

Oh, yeah, almost certainly.

I didn't think people would do add attributes to the test instances for pytest style test cases because they could just use fixtures. I'll put together a second PR for non-unittest cases.

[nicoddemus]

@d-b-w, I did try out your branch with this code:

import unittest

class ExpensiveObject(object):

    def __del__(self):
        print('ExpensiveObject deleted')

class TestCaseObjectsShouldBeCleanedUp(unittest.TestCase):

    def setUp(self):
        print('Created')
        self.an_expensive_object = ExpensiveObject()

    def test_demo(self):
        pass

    def test_demo2(self):
        pass    

On master:

$ pytest foo.py -s -q
Created
.Created
.
2 passed in 0.03 seconds

On your branch:

$ pytest foo.py -s -q
Created
.ExpensiveObject deleted
Created
.ExpensiveObject deleted

2 passed in 0.03 seconds

So it seems to work just fine, thanks for this. 😁

@The-Compiler, you got a point:

class ExpensiveObject(object):

    def __del__(self):
        print('ExpensiveObject deleted')

class TestCaseObjectsShouldBeCleanedUp(object):

    def setup_method(self, m):
        print('Created')
        self.an_expensive_object = ExpensiveObject()

    def test_demo(self):
        pass

    def test_demo2(self):
        pass    

$ pytest foo.py -s -q
Created
.Created
.
2 passed in 0.03 seconds

So we should probably do something similar for normal test instances.

@d-b-w would be willing to work on that as well? Otherwise I would rather we merge this as it is because it is already an improvement and create a separate issue.

[nicoddemus]

I didn't think people would do add attributes to the test instances for pytest style test cases because they could just use fixtures. I'll put together a second PR for non-unittest cases.

Oh sorry I didn't see your reply before I posted mine. I will merge this as it is then if you prefer a separate PR.

Thanks again!

[d-b-w]

Heh - I'm accustomed to making my commits as small as they can be and still be functional. I suppose that for contributions to pytest, PRs should resolve complete issues/ or be complete lines on the release notes :)

[nicoddemus]

No problem at all having two separate PRs for this. I went ahead and merged because I don't know when you can find time to also work on the issue of the non-unittest cases so I thought best to get this into master right away. 😁

[d-b-w]

I'm having some trouble with the fix for non-unittest tests - when I add a teardown to the Instance class, the nose generator tests fail (from python.py):

class Instance(PyCollector):
    ...
    def teardown(self):
         self.obj = None

The failure message:

test_nose_test_generator_fixtures.py .....FFFFF
______________________________ TestClass.test[0] _______________________________

self = <test_nose_test_generator_fixtures.TestClass object at 0x103ac8190>
i = 0

 def check(self, i):
     print ("check called in %s" % self)
     expect = ['setup']
     #for x in range(0, i):
     #    expect.append('setup')
     #    expect.append('teardown')
     #expect.append('setup')

  eq_(self.called, expect)

E AttributeError: 'TestClass' object has no attribute 'called'

I think this means that the setup wasn't performed for some of the tests?