Add test for dynamic updates, keep timestamps as floats

traitlets/config/application.py

@@ -316,7 +316,7 @@ def __init__(self, **kwargs):
             else:
                 self.classes.insert(0, self.__class__)
 
-        self.last_config_update = int(time.time())
+        self.last_config_update = time.time()
         self.dynamic_configurables = {}
 
     @observe('config')
@@ -832,7 +832,7 @@ def _config_files_updated(self):
         """
         updated = False
         for file in self._loaded_config_files:
-            mod_time = int(os.path.getmtime(file))
+            mod_time = os.path.getmtime(file)
             if mod_time > self.last_config_update:
                 self.log.debug("Config file was updated: {}!".format(file))
                 self.last_config_update = mod_time

traitlets/config/tests/test_application.py

@@ -358,7 +358,6 @@ def test_warn_autocorrect(self):
         self.assertIn("warn_typo", stream.getvalue())
         self.assertIn("warn_tpyo", stream.getvalue())
 
-
     def test_flatten_flags(self):
         cfg = Config()
         cfg.MyApp.log_level = logging.WARN
@@ -547,6 +546,45 @@ def test_subcommands_instanciation(self):
         self.assertIs(app.subapp.parent, app)
         self.assertIs(app.subapp.subapp.parent, app.subapp)     # Set by factory.
 
+    def test_dynamic_updates(self):
+        app = MyApp()
+        app.log = logging.getLogger()
+        name = 'config.py'
+        with TemporaryDirectory('_1') as td1:
+            with open(pjoin(td1, name), 'w') as f:
+                f.writelines([
+                    "c.MyApp.running = True\n",
+                    "c.MyApp.Bar.b = 1\n"
+                ])
+
+            app.load_config_file(name, path=[td1])
+            app.init_bar()
+            app.add_dynamic_configurable("MyApp", app)
+            app.add_dynamic_configurable("Bar", app.bar)
+            with self.assertRaises(RuntimeError):
+                app.add_dynamic_configurable("Bogus", app.log)
+
+            app.start()
+            self.assertEqual(app.running, True)
+            self.assertEqual(app.bar.b, 1)
+
+            # update config file
+            with open(pjoin(td1, name), 'w') as f:
+                f.writelines([
+                    "c.MyApp.running = False\n",
+                    "c.MyApp.Bar.b = 2\n"
+                ])
+
+            # trigger reload and verify updates
+            app.update_dynamic_configurables()
+            self.assertEqual(app.running, False)
+            self.assertEqual(app.bar.b, 2)
+
+            # repeat to ensure no unexpected changes occurred
+            app.update_dynamic_configurables()
+            self.assertEqual(app.running, False)
+            self.assertEqual(app.bar.b, 2)
+
 
 class Root(Application):
     subcommands = {