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

Dan Wandschneider · Dan Wandschneider · commit e46e653794e3 · 2016-11-07T18:32:56.000-08:00
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.
diff --git a/AUTHORS b/AUTHORS
@@ -36,6 +36,7 @@ Christopher Gilling
 Daniel Grana
 Daniel Hahler
 Daniel Nuri
+Daniel Wandschneider
 Danielle Jenkins
 Dave Hunt
 David Díaz-Barquero
diff --git a/CHANGELOG.rst b/CHANGELOG.rst
@@ -26,7 +26,8 @@
 * Properly handle exceptions in ``multiprocessing`` tasks (`#1984`_).
   Thanks `@adborden`_ for the report and `@nicoddemus`_ for the PR.
 
-*
+* Clean up unittest TestCase objects after tests are complete (`#1649`_).
+  Thanks `@d_b_w`_ for the report and PR.
 
 *
 
@@ -38,13 +39,15 @@
 .. _@okulynyak: https://github.com/okulynyak
 .. _@matclab: https://github.com/matclab
 .. _@gdyuldin: https://github.com/gdyuldin
+.. _@d_b_w: https://github.com/d_b_w
 
 .. _#442: https://github.com/pytest-dev/pytest/issues/442
 .. _#1976: https://github.com/pytest-dev/pytest/issues/1976
 .. _#1984: https://github.com/pytest-dev/pytest/issues/1984
 .. _#1998: https://github.com/pytest-dev/pytest/issues/1998
 .. _#2004: https://github.com/pytest-dev/pytest/issues/2004
 .. _#2005: https://github.com/pytest-dev/pytest/issues/2005
+.. _#1649: https://github.com/pytest-dev/pytest/issues/1649
 
 
 3.0.3
diff --git a/_pytest/unittest.py b/_pytest/unittest.py
@@ -94,6 +94,9 @@ def _fix_unittest_skip_decorator(self):
     def teardown(self):
         if hasattr(self._testcase, 'teardown_method'):
             self._testcase.teardown_method(self._obj)
+        # Allow garbage collection on TestCase instance attributes.
+        self._testcase = None
+        self._obj = None
 
     def startTest(self, testcase):
         pass
diff --git a/testing/test_unittest.py b/testing/test_unittest.py
@@ -1,5 +1,6 @@
 from _pytest.main import EXIT_NOTESTSCOLLECTED
 import pytest
+import gc
 
 def test_simple_unittest(testdir):
     testpath = testdir.makepyfile("""
@@ -134,6 +135,28 @@ def test_check(self):
     assert passed == 2
     assert passed + skipped + failed == 2
 
+def test_teardown_issue1649(testdir):
+    """
+    Are TestCase objects cleaned up? Often unittest TestCase objects set
+    attributes that are large and expensive during setUp.
+
+    The TestCase will not be cleaned up if the test fails, because it
+    would then exist in the stackframe.
+    """
+    testpath = testdir.makepyfile("""
+        import unittest
+        class TestCaseObjectsShouldBeCleanedUp(unittest.TestCase):
+            def setUp(self):
+                self.an_expensive_object = 1
+            def test_demo(self):
+                pass
+
+    """)
+    testdir.inline_run("-s", testpath)
+    gc.collect()
+    for obj in gc.get_objects():
+        assert type(obj).__name__ != 'TestCaseObjectsShouldBeCleanedUp'
+
 @pytest.mark.skipif("sys.version_info < (2,7)")
 def test_unittest_skip_issue148(testdir):
     testpath = testdir.makepyfile("""
