test: Make the tests pass in pytest-asyncio>=0.17 (#525)

Fixes #518

Unpin pytest-asyncio version.
Adjust the event_loop fixture to make it compatible with pytest-asyncio>=0.17
Use the @pytest_asyncio.fixture decorator for apropriately.

Author: Mariatta

packages/google-cloud-firestore/noxfile.py

@@ -108,7 +108,7 @@ def default(session):
         "asyncmock",
         "pytest",
         "pytest-cov",
-        "pytest-asyncio<0.17.0",
+        "pytest-asyncio",
         "-c",
         constraints_path,
     )
@@ -214,7 +214,7 @@ def system(session):
         "mock",
         "pytest",
         "google-cloud-testutils",
-        "pytest-asyncio<0.17.0",
+        "pytest-asyncio",
         "-c",
         constraints_path,
     )

packages/google-cloud-firestore/tests/system/test_system_async.py

@@ -17,6 +17,7 @@
 import itertools
 import math
 import pytest
+import pytest_asyncio
 import operator
 from typing import Callable, Dict, List, Optional
 
@@ -40,7 +41,6 @@
     FIRESTORE_EMULATOR,
 )
 
-_test_event_loop = asyncio.new_event_loop()
 pytestmark = pytest.mark.asyncio
 
 
@@ -62,7 +62,7 @@ def client():
     yield firestore.AsyncClient(project=project, credentials=credentials)
 
 
-@pytest.fixture
+@pytest_asyncio.fixture
 async def cleanup():
     operations = []
     yield operations.append
@@ -71,10 +71,13 @@ async def cleanup():
         await operation()
 
 
-@pytest.fixture
+@pytest.fixture(scope="module")
 def event_loop():
-    asyncio.set_event_loop(_test_event_loop)
-    return asyncio.get_event_loop()
+    """Change event_loop fixture to module level."""
+    policy = asyncio.get_event_loop_policy()
+    loop = policy.new_event_loop()
+    yield loop
+    loop.close()
 
 
 async def test_collections(client):
@@ -546,7 +549,7 @@ async def test_collection_add(client, cleanup):
     assert set([i async for i in collection3.list_documents()]) == {document_ref5}
 
 
-@pytest.fixture
+@pytest_asyncio.fixture
 async def query_docs(client):
     collection_id = "qs" + UNIQUE_RESOURCE_ID
     sub_collection = "child" + UNIQUE_RESOURCE_ID