Catch warnings in inactive tg test and update docs

Doc/library/asyncio-task.rst

@@ -334,6 +334,9 @@ and reliable way to wait for all tasks in the group to finish.
 
       Create a task in this task group.
       The signature matches that of :func:`asyncio.create_task`.
+      If the task group is inactive (e.g. not yet entered,
+      already finished, or in the process of shutting down),
+      we will close the given ``coro``.
 
       .. versionchanged:: 3.13
 

Doc/whatsnew/3.13.rst

@@ -187,7 +187,8 @@ Other Language Changes
 
 * When :func:`asyncio.TaskGroup.create_task` is called on an inactive
   :class:`asyncio.TaskGroup`, the given coroutine will be closed (which
-  prevents a :exc:`RuntimeWarning`).
+  prevents a :exc:`RuntimeWarning` about the given coroutine being
+  never awaited).
 
   (Contributed by Arthur Tacca and Jason Zhang in :gh:`115957`.)
 

Lib/test/test_asyncio/test_taskgroups.py

@@ -7,6 +7,7 @@
 import contextlib
 from asyncio import taskgroups
 import unittest
+import warnings
 
 from test.test_asyncio.utils import await_without_task
 
@@ -794,12 +795,19 @@ async def test_taskgroup_double_enter(self):
                 pass
 
     async def test_taskgroup_finished(self):
-        tg = taskgroups.TaskGroup()
-        async with tg:
-            pass
-        coro = asyncio.sleep(0)
-        with self.assertRaisesRegex(RuntimeError, "is finished"):
-            tg.create_task(coro)
+        async def create_task_after_tg_finish():
+            tg = taskgroups.TaskGroup()
+            async with tg:
+                pass
+            coro = asyncio.sleep(0)
+            with self.assertRaisesRegex(RuntimeError, "is finished"):
+                tg.create_task(coro)
+
+        # Make sure the coroutine was closed when submitted to the inactive tg
+        # (if not closed, a RuntimeWarning should have been raised)
+        with warnings.catch_warnings(record=True) as w:
+            await create_task_after_tg_finish()
+        self.assertEqual(len(w), 0)
 
     async def test_taskgroup_not_entered(self):
         tg = taskgroups.TaskGroup()