[#781] modify access_time test with guaranteed passing assertions

The test now fetches the modify and access timestamps during the interval
in which the replica is open, then asserts those timestamps as equal to
each other, as well as that they are greater than a system-generated
datetime of about two seconds prior.  (This is due to some timestamps
including a microseconds count whereas others do not.)

Author: d-w-moore

irods/test/data_obj_test.py

@@ -65,7 +65,7 @@ def is_localhost_synonym(name):
 from irods.manager import data_object_manager
 from irods.message import RErrorStack
 from irods.message import ET, XML_Parser_Type, default_XML_parser, current_XML_parser
-from datetime import datetime
+from datetime import datetime, timezone, timedelta
 from tempfile import NamedTemporaryFile, gettempdir, mktemp
 from irods.test.helpers import unique_name, my_function_name
 from irods.ticket import Ticket
@@ -3305,16 +3305,20 @@ def test_access_time__issue_700(self):
         if self.sess.server_version < (5,):
             self.skipTest("iRODS servers < 5.0.0 do not provide an access_time attribute for data objects.")
 
-        data_path= iRODSPath(self.coll.path,
-            unique_name(my_function_name(), datetime.now())
-            )
-        with self.sess.data_objects.open(data_path,"w") as f:
-            f.write(b'_')
-        with self.sess.data_objects.open(data_path,"r") as f:
-            f.read()
+        prior_ts = datetime.now(timezone.utc) - timedelta(seconds=2)
+
+        # Create a new, uniquely named test data object.
+        data = self.sess.data_objects.create(
+            logical_path:=f'{helpers.home_collection(self.sess)}/{unique_name(my_function_name(), datetime.now())}'
+        )
+
+        with data.open('w') as f:
+            data = self.sess.data_objects.get(logical_path)
+            self.assertEqual(data.access_time, data.modify_time)
+            self.assertGreaterEqual(data.access_time, prior_ts)
 
-        data = self.sess.data_objects.get(data_path)
-        self.assertGreaterEqual(data.access_time, data.modify_time)
+        # Test that access_time is there, and of the right type.
+        self.assertIs(type(data.access_time), datetime)
 
 if __name__ == "__main__":
     # let the tests find the parent irods lib