added system test with python datetimes

Author: gkevinzheng

tests/system/test_system.py

@@ -1142,7 +1142,10 @@ def test_collection_add(client, cleanup, database):
 
 
 @pytest.mark.parametrize("database", [None, FIRESTORE_OTHER_DB], indirect=True)
-def test_list_collections_with_read_time(client, cleanup, database):
+@pytest.mark.parametrize(
+    "use_python_datetime", [True, False]
+)
+def test_list_collections_with_read_time(client, cleanup, database, use_python_datetime):
     # TODO(microgen): list_documents is returning a generator, not a list.
     # Consider if this is desired. Also, Document isn't hashable.
     collection_id = "coll-add" + UNIQUE_RESOURCE_ID
@@ -1152,11 +1155,15 @@ def test_list_collections_with_read_time(client, cleanup, database):
 
     data1 = {"foo": "bar"}
     update_time1, document_ref1 = collection.add(data1)
+    if use_python_datetime:
+        update_time1 = datetime.datetime.now(tz=datetime.timezone.utc)
     cleanup(document_ref1.delete)
     assert set(collection.list_documents()) == {document_ref1}
 
     data2 = {"bar": "baz"}
     update_time2, document_ref2 = collection.add(data2)
+    if use_python_datetime:
+        update_time2 = datetime.datetime.now(tz=datetime.timezone.utc)
     cleanup(document_ref2.delete)
     assert set(collection.list_documents()) == {document_ref1, document_ref2}
     assert set(collection.list_documents(read_time=update_time1)) == {document_ref1}