bpo-41322: Add unit tests for deprecation of test return values (GH-27846)

Also fix the traceback of warnings.

1 files changed, 20 insertions, 0 deletions

diff --git a/Lib/unittest/test/test_case.py b/Lib/unittest/test/test_case.py
index b8aca92a8e..f3cabe44d1 100644
--- a/Lib/unittest/test/test_case.py
+++ b/Lib/unittest/test/test_case.py
@@ -306,6 +306,26 @@ class Test_TestCase(unittest.TestCase, TestEquality, TestHashing):
 
         Foo('test').run()
 
+    def test_deprecation_of_return_val_from_test(self):
+        # Issue 41322 - deprecate return of value!=None from a test
+        class Foo(unittest.TestCase):
+            def test1(self):
+                return 1
+            def test2(self):
+                yield 1
+
+        with self.assertWarns(DeprecationWarning) as w:
+            Foo('test1').run()
+        self.assertIn('It is deprecated to return a value!=None', str(w.warnings[0].message))
+        self.assertIn('test1', str(w.warnings[0].message))
+        self.assertEqual(w.warnings[0].filename, __file__)
+
+        with self.assertWarns(DeprecationWarning) as w:
+            Foo('test2').run()
+        self.assertIn('It is deprecated to return a value!=None', str(w.warnings[0].message))
+        self.assertIn('test2', str(w.warnings[0].message))
+        self.assertEqual(w.warnings[0].filename, __file__)
+
     def _check_call_order__subtests(self, result, events, expected_events):
         class Foo(Test.LoggingTestCase):
             def test(self):