ERP5TypeTestCase: support using unpinDateTime as a context manager

exiting the context manager restores the original DateTime behavior

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

@@ -190,6 +190,14 @@ class TestPinDateTime(ERP5TypeTestCase):
     self.unpinDateTime()
     self.assertGreaterEqual(DateTime(), actual_begin_date)
 
+  def test_pinDateTime_context_manager(self):
+    actual_begin_date = DateTime()
+    datetime = DateTime('2001/01/01 01:01:01')
+
+    with self.pinDateTime(datetime):
+      self.assertEqual(DateTime(), datetime)
+    self.assertGreaterEqual(DateTime(), actual_begin_date)
+
 
 def test_suite():
   suite = unittest.TestSuite()

product/ERP5Type/tests/ERP5TypeTestCase.py

@@ -372,12 +372,25 @@ class ERP5TypeTestCaseMixin(ProcessingNodeTestCase, PortalTestCase):
 
     def pinDateTime(self, date_time):
       # pretend time has stopped at a certain date (i.e. the test runs
-      # infinitely fast), to avoid errors on tests that are started
+      # 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
+      # reset.
       global _pinned_date_time
       assert date_time is None or isinstance(date_time, DateTime)
       _pinned_date_time = date_time
 
+      unpinDateTime = self.unpinDateTime
+      class UnpinContextManager(object):
+        def __enter__(self):
+          return self
+        def __exit__(self, *args):
+          unpinDateTime()
+      return UnpinContextManager()
+
+    def unpinDateTime(self):
+      self.pinDateTime(None)
+
     def setTimeZoneToUTC(self):
       # Make sure tests runs with UTC timezone. Some tests are checking values
       # based on now, and this could give unexpected results:
@@ -389,9 +402,6 @@ class ERP5TypeTestCaseMixin(ProcessingNodeTestCase, PortalTestCase):
       DateTime._isDST = False
       DateTime._localzone = DateTime._localzone0 = DateTime._localzone1 = "UTC"
 
-    def unpinDateTime(self):
-      self.pinDateTime(None)
-
     def getDefaultSystemPreference(self):
       id = 'default_system_preference'
       tool = self.getPreferenceTool()