fix: add eager task factory tests

tests/test_eager_task_factory.py

@@ -0,0 +1,89 @@
+"""Tests staggered_race and eager_task_factory with asyncio.Task."""
+
+import asyncio
+import sys
+import unittest
+
+from aiohappyeyeballs._staggered import staggered_race
+
+
+def tearDownModule():
+    asyncio.set_event_loop_policy(None)
+
+
+class EagerTaskFactoryLoopTests(unittest.TestCase):
+
+    def close_loop(self, loop):
+        loop.close()
+
+    def set_event_loop(self, loop, *, cleanup=True):
+        if loop is None:
+            raise AssertionError("loop is None")
+        # ensure that the event loop is passed explicitly in asyncio
+        asyncio.set_event_loop(None)
+        if cleanup:
+            self.addCleanup(self.close_loop, loop)
+
+    def tearDown(self):
+        asyncio.set_event_loop(None)
+        self.doCleanups()
+
+    def setUp(self):
+        super().setUp()
+        self.loop = asyncio.new_event_loop()
+        self.eager_task_factory = asyncio.create_eager_task_factory(asyncio.Task)  # type: ignore
+        self.loop.set_task_factory(self.eager_task_factory)
+        self.set_event_loop(self.loop)
+
+    def test_staggered_race_with_eager_tasks(self):
+        # See https://github.com/python/cpython/issues/124309
+
+        async def fail():
+            await asyncio.sleep(0)
+            raise ValueError("no good")
+
+        async def run():
+            winner, index, excs = await staggered_race(
+                [
+                    lambda: asyncio.sleep(2, result="sleep2"),
+                    lambda: asyncio.sleep(1, result="sleep1"),
+                    lambda: fail(),
+                ],
+                delay=0.25,
+            )
+            self.assertEqual(winner, "sleep1")
+            self.assertEqual(index, 1)
+            assert index is not None
+            self.assertIsNone(excs[index])
+            self.assertIsInstance(excs[0], asyncio.CancelledError)
+            self.assertIsInstance(excs[2], ValueError)
+
+        self.loop.run_until_complete(run())
+
+    def test_staggered_race_with_eager_tasks_no_delay(self):
+        # See https://github.com/python/cpython/issues/124309
+        async def fail():
+            raise ValueError("no good")
+
+        async def run():
+            winner, index, excs = await staggered_race(
+                [
+                    lambda: fail(),
+                    lambda: asyncio.sleep(1, result="sleep1"),
+                    lambda: asyncio.sleep(0, result="sleep0"),
+                ],
+                delay=None,
+            )
+            self.assertEqual(winner, "sleep1")
+            self.assertEqual(index, 1)
+            assert index is not None
+            self.assertIsNone(excs[index])
+            self.assertIsInstance(excs[0], ValueError)
+            self.assertEqual(len(excs), 2)
+
+        self.loop.run_until_complete(run())
+
+
+if __name__ == "__main__":
+    if sys.version_info >= (3, 12):
+        unittest.main()