Fixed #26942 -- Added support for subtests during parallel testing.

3 files changed, 105 insertions, 4 deletions

diff --git a/django/test/runner.py b/django/test/runner.py
index 02a4c826ac..0610d303f8 100644
--- a/django/test/runner.py
+++ b/django/test/runner.py
@@ -77,6 +77,9 @@ class RemoteTestResult(object):
     """
 
     def __init__(self):
+        if tblib is not None:
+            tblib.pickling_support.install()
+
         self.events = []
         self.failfast = False
         self.shouldStop = False
@@ -86,6 +89,22 @@ class RemoteTestResult(object):
     def test_index(self):
         return self.testsRun - 1
 
+    def _print_unpicklable_subtest(self, test, subtest, pickle_exc):
+        print("""
+Subtest failed:
+
+    test: {}
+ subtest: {}
+
+Unfortunately, the subtest that failed cannot be pickled, so the parallel
+test runner cannot handle it cleanly. Here is the pickling error:
+
+> {}
+
+You should re-run this test with --parallel=1 to reproduce the failure
+with a cleaner failure message.
+""".format(test, subtest, pickle_exc))
+
     def check_picklable(self, test, err):
         # Ensure that sys.exc_info() tuples are picklable. This displays a
         # clear multiprocessing.pool.RemoteTraceback generated in the child
@@ -133,6 +152,13 @@ failure and get a correct traceback.
 """.format(test, original_exc_txt, pickle_exc_txt))
             raise
 
+    def check_subtest_picklable(self, test, subtest):
+        try:
+            pickle.dumps(subtest)
+        except Exception as exc:
+            self._print_unpicklable_subtest(test, subtest, exc)
+            raise
+
     def stop_if_failfast(self):
         if self.failfast:
             self.stop()
@@ -164,7 +190,15 @@ failure and get a correct traceback.
         self.stop_if_failfast()
 
     def addSubTest(self, test, subtest, err):
-        raise NotImplementedError("subtests aren't supported at this time")
+        # Follow Python 3.5's implementation of unittest.TestResult.addSubTest()
+        # by not doing anything when a subtest is successful.
+        if err is not None:
+            # Call check_picklable() before check_subtest_picklable() since
+            # check_picklable() performs the tblib check.
+            self.check_picklable(test, err)
+            self.check_subtest_picklable(test, subtest)
+            self.events.append(('addSubTest', self.test_index, subtest, err))
+            self.stop_if_failfast()
 
     def addSuccess(self, test):
         self.events.append(('addSuccess', self.test_index))
@@ -307,9 +341,6 @@ class ParallelTestSuite(unittest.TestSuite):
         Even with tblib, errors may still occur for dynamically created
         exception classes such Model.DoesNotExist which cannot be unpickled.
         """
-        if tblib is not None:
-            tblib.pickling_support.install()
-
         counter = multiprocessing.Value(ctypes.c_int, 0)
         pool = multiprocessing.Pool(
             processes=self.processes,
diff --git a/docs/releases/1.11.txt b/docs/releases/1.11.txt
index 498b3ee09f..c8282f70d6 100644
--- a/docs/releases/1.11.txt
+++ b/docs/releases/1.11.txt
@@ -313,6 +313,9 @@ Tests
   ``django.test.runner``) and :func:`~django.test.utils.teardown_databases`
   functions make it easier to build custom test runners.
 
+* Added support for :meth:`python:unittest.TestCase.subTest`’s when using the
+  :option:`test --parallel` option.
+
 URLs
 ~~~~
 
diff --git a/tests/test_runner/test_parallel.py b/tests/test_runner/test_parallel.py
new file mode 100644
index 0000000000..529fe22092
--- /dev/null
+++ b/tests/test_runner/test_parallel.py
@@ -0,0 +1,67 @@
+import unittest
+
+from django.test import SimpleTestCase
+from django.test.runner import RemoteTestResult
+from django.utils import six
+
+try:
+    import tblib
+except ImportError:
+    tblib = None
+
+
+class ParallelTestRunnerTest(SimpleTestCase):
+    """
+    End-to-end tests of the parallel test runner.
+
+    These tests are only meaningful when running tests in parallel using
+    the --parallel option, though it doesn't hurt to run them not in
+    parallel.
+    """
+
+    @unittest.skipUnless(six.PY3, 'subtests were added in Python 3.4')
+    def test_subtest(self):
+        """
+        Check that passing subtests work.
+        """
+        for i in range(2):
+            with self.subTest(index=i):
+                self.assertEqual(i, i)
+
+
+class SampleFailingSubtest(SimpleTestCase):
+
+    # This method name doesn't begin with "test" to prevent test discovery
+    # from seeing it.
+    def dummy_test(self):
+        """
+        A dummy test for testing subTest failures.
+        """
+        for i in range(3):
+            with self.subTest(index=i):
+                self.assertEqual(i, 1)
+
+
+class RemoteTestResultTest(SimpleTestCase):
+
+    @unittest.skipUnless(six.PY3 and tblib is not None, 'requires tblib to be installed')
+    def test_add_failing_subtests(self):
+        """
+        Failing subtests are added correctly using addSubTest().
+        """
+        # Manually run a test with failing subtests to prevent the failures
+        # from affecting the actual test run.
+        result = RemoteTestResult()
+        subtest_test = SampleFailingSubtest(methodName='dummy_test')
+        subtest_test.run(result=result)
+
+        events = result.events
+        self.assertEqual(len(events), 4)
+
+        event = events[1]
+        self.assertEqual(event[0], 'addSubTest')
+        self.assertEqual(str(event[2]), 'dummy_test (test_runner.test_parallel.SampleFailingSubtest) (index=0)')
+        self.assertEqual(repr(event[3][1]), "AssertionError('0 != 1',)")
+
+        event = events[2]
+        self.assertEqual(repr(event[3][1]), "AssertionError('2 != 1',)")