tests: fix DateTime.isPast() under pinDateTime

When under a pinDateTime context, d.isPast() was comparing d with the
actual current date, not the fake date from the pinned context.

Also, make the methods class methods, so that they can be used as
external methods in Zelenium tests.

bt5/erp5_core_test/TestTemplateItem/portal_components/test.erp5.testDateUtils.py

@@ -208,6 +208,7 @@ class TestPinDateTime(ERP5TypeTestCase):
 
     self.pinDateTime(datetime)
     self.assertEqual(DateTime(), datetime)
+    self.assertEqual(DateTime(None), datetime)
     self.assertEqual(DateTime('2002/02/02 02:02:02 GMT+2'), fixed_date_with_timezone)
 
     self.unpinDateTime()
@@ -221,6 +222,24 @@ class TestPinDateTime(ERP5TypeTestCase):
       self.assertEqual(DateTime(), datetime)
     self.assertGreaterEqual(DateTime(), actual_begin_date)
 
+  def test_pinDateTime_date_time_methods(self):
+    with self.pinDateTime(DateTime('2001/01/01 01:01:01')):
+      self.assertTrue(DateTime('2000').isPast())
+      self.assertTrue(DateTime('2002').isFuture())
+      self.assertTrue(DateTime('2001').isCurrentYear())
+      self.assertTrue(DateTime('2001/01/02 01:01:01').isCurrentMonth())
+      self.assertTrue(DateTime('2001/01/01 02:01:01').isCurrentDay())
+      self.assertTrue(DateTime().strftime('%Y'), '2001')
+      self.assertTrue(DateTime('2002').strftime('%Y'), '2001')
+
+  def test_pinDateTime_timezone(self):
+    with self.pinDateTime(DateTime('2001/01/01 01:01:01 GMT+9')):
+      self.assertEqual(DateTime().timezone(), 'GMT+9')
+      self.assertEqual(DateTime('2001/01/01 01:01:01 GMT+4').timezone(), 'GMT+4')
+    with self.pinDateTime(DateTime('2001/01/01 01:01:01 Europe/Paris')):
+      self.assertEqual(DateTime().timezone(), 'Europe/Paris')
+      self.assertEqual(DateTime('2001/01/01 01:01:01 GMT+4').timezone(), 'GMT+4')
+
 
 class TestTimeZoneContext(ERP5TypeTestCase):
   def afterSetUp(self):

product/ERP5Type/tests/ERP5TypeTestCase.py

@@ -189,6 +189,7 @@ def profile_if_environ(environment_var_name):
 assert getattr(DateTime, '_original_parse_args', None) is None
 DateTime._original_parse_args = DateTime._parse_args
 
+_datetime_system_time_patcher = None
 _pinned_date_time = None
 
 def _parse_args(self, *args, **kw):
@@ -368,26 +369,38 @@ class ERP5TypeTestCaseMixin(ProcessingNodeTestCase, PortalTestCase, functional.F
       if not uf.getUserById(user_name):
         uf._doAddUser(user_name, self.newPassword(), ['Member'], [])
 
-    def pinDateTime(self, date_time):
+    @classmethod
+    def pinDateTime(cls, date_time):
       # pretend time has stopped at a certain date (i.e. the test runs
       # infinitely fast), for example to avoid errors on tests that are started
       # just before midnight.
-      # This can be used as a context manager, otherwise use unpinDateTime to
+      # This is best used as a context manager, otherwise use unpinDateTime to
       # reset.
-      global _pinned_date_time
+      global _pinned_date_time, _datetime_system_time_patcher
       assert date_time is None or isinstance(date_time, DateTime)
       _pinned_date_time = date_time
 
-      unpinDateTime = self.unpinDateTime
+      if _datetime_system_time_patcher is not None:
+        _datetime_system_time_patcher.stop()
+      if date_time is not None:
+        _datetime_system_time_patcher = mock.patch.object(
+          sys.modules['DateTime.DateTime'],
+          '_system_time',
+          return_value=date_time.timeTime())
+        _datetime_system_time_patcher.start()
+
+      unpinDateTime = cls.unpinDateTime
       class UnpinContextManager(object):
         def __enter__(self):
           return self
         def __exit__(self, *args):
           unpinDateTime()
+          _datetime_system_time_patcher.stop()
       return UnpinContextManager()
 
-    def unpinDateTime(self):
-      self.pinDateTime(None)
+    @classmethod
+    def unpinDateTime(cls):
+      cls.pinDateTime(None)
 
     def setTimeZoneToUTC(self):
       # Deprecated, prefer using `timeZoneContext` context manager instead.