tests: Do set_event_loop(None) in unittests

uvloop should consistently pass around the loop reference in its
internal APIs.

Even though explicit passing of event loop objects is discouraged
in asyncio programs, uvloop itself is too low-level to rely on
get_event_loop.

tests/test_aiohttp.py

@@ -6,6 +6,7 @@ except ImportError:
 else:
     skip_tests = False
 
+import asyncio
 import unittest
 
 from uvloop import _testbase as tb
@@ -29,6 +30,8 @@ class _TestAioHTTP:
                 response.write(PAYLOAD)
                 await response.write_eof()
 
+        asyncio.set_event_loop(self.loop)
+
         f = self.loop.create_server(
             lambda: HttpRequestHandler(keepalive_timeout=1),
             '0.0.0.0', '0')

tests/test_base.py

@@ -149,9 +149,9 @@ class _TestBase:
         # libuv cached time.
 
         async def main():
-            await asyncio.sleep(0.001)
+            await asyncio.sleep(0.001, loop=self.loop)
             time.sleep(0.01)
-            await asyncio.sleep(0.01)
+            await asyncio.sleep(0.01, loop=self.loop)
 
         started = time.monotonic()
         self.loop.run_until_complete(main())

tests/test_executors.py

@@ -21,7 +21,7 @@ class _TestExecutors:
                     coros.append(self.loop.run_in_executor(pool, fib, i))
                 res = await asyncio.gather(*coros, loop=self.loop)
             self.assertEqual(res, fib10)
-            await asyncio.sleep(0.01)
+            await asyncio.sleep(0.01, loop=self.loop)
 
         fib10 = [fib(i) for i in range(10)]
         self.loop.run_until_complete(run())

tests/test_tcp.py

@@ -708,7 +708,7 @@ class Test_UV_TCP(_TestTCP, tb.UVTestCase):
             self.loop.create_task(run())
             self.loop.run_until_complete(srv.wait_closed())
             gc.collect()
-            self.loop.run_until_complete(asyncio.sleep(0.1))
+            self.loop.run_until_complete(asyncio.sleep(0.1, loop=self.loop))
 
         # Since one TCPTransport handle wasn't closed correctly,
         # we need to disable this check:

uvloop/_testbase.py

@@ -2,6 +2,7 @@
 
 
 import asyncio
+import asyncio.events
 import collections
 import contextlib
 import gc
@@ -68,12 +69,20 @@ class BaseTestCase(unittest.TestCase, metaclass=BaseTestCaseMeta):
 
     def setUp(self):
         self.loop = self.new_loop()
-        asyncio.set_event_loop(self.loop)
+        asyncio.set_event_loop(None)
         self._check_unclosed_resources_in_debug = True
 
+        if hasattr(asyncio, '_get_running_loop'):
+            # Disable `_get_running_loop`.
+            self._get_running_loop = asyncio.events._get_running_loop
+            asyncio.events._get_running_loop = lambda: None
+
     def tearDown(self):
         self.loop.close()
 
+        if hasattr(asyncio, '_get_running_loop'):
+            asyncio.events._get_running_loop = self._get_running_loop
+
         if not self._check_unclosed_resources_in_debug:
             return
 
@@ -199,6 +208,17 @@ class UVTestCase(BaseTestCase):
 
 class AIOTestCase(BaseTestCase):
 
+    def setUp(self):
+        super().setUp()
+
+        watcher = asyncio.SafeChildWatcher()
+        watcher.attach_loop(self.loop)
+        asyncio.set_child_watcher(watcher)
+
+    def tearDown(self):
+        asyncio.set_child_watcher(None)
+        super().tearDown()
+
     def new_loop(self):
         return asyncio.new_event_loop()