bpo-47038: Rewrite missed asyncio.wait_for test to use IsolatedAnsyncioTestCase (GH-31946)

(cherry picked from commit 3dd9bfa)

Co-authored-by: Andrew Svetlov <andrew.svetlov@gmail.com>

Author: miss-islington

Lib/test/test_asyncio/test_tasks.py

@@ -2188,32 +2188,6 @@ def test_task_source_traceback(self):
                           'test_task_source_traceback'))
         self.loop.run_until_complete(task)
 
-    def _test_cancel_wait_for(self, timeout):
-        loop = asyncio.new_event_loop()
-        self.addCleanup(loop.close)
-
-        async def blocking_coroutine():
-            fut = self.new_future(loop)
-            # Block: fut result is never set
-            await fut
-
-        task = loop.create_task(blocking_coroutine())
-
-        wait = loop.create_task(asyncio.wait_for(task, timeout))
-        loop.call_soon(wait.cancel)
-
-        self.assertRaises(asyncio.CancelledError,
-                          loop.run_until_complete, wait)
-
-        # Python issue #23219: cancelling the wait must also cancel the task
-        self.assertTrue(task.cancelled())
-
-    def test_cancel_blocking_wait_for(self):
-        self._test_cancel_wait_for(None)
-
-    def test_cancel_wait_for(self):
-        self._test_cancel_wait_for(60.0)
-
     def test_cancel_gather_1(self):
         """Ensure that a gathering future refuses to be cancelled once all
         children are done"""

Lib/test/test_asyncio/test_waitfor.py

@@ -264,6 +264,30 @@ async def inner():
 
         self.assertEqual(await inner_task, 42)
 
+    async def _test_cancel_wait_for(self, timeout):
+        loop = asyncio.get_running_loop()
+
+        async def blocking_coroutine():
+            fut = loop.create_future()
+            # Block: fut result is never set
+            await fut
+
+        task = asyncio.create_task(blocking_coroutine())
+
+        wait = asyncio.create_task(asyncio.wait_for(task, timeout))
+        loop.call_soon(wait.cancel)
+
+        with self.assertRaises(asyncio.CancelledError):
+            await wait
+
+        # Python issue #23219: cancelling the wait must also cancel the task
+        self.assertTrue(task.cancelled())
+
+    async def test_cancel_blocking_wait_for(self):
+        await self._test_cancel_wait_for(None)
+
+    async def test_cancel_wait_for(self):
+        await self._test_cancel_wait_for(60.0)
 
 
 if __name__ == '__main__':