Add a helper for testing restart on changed

Most api charms test restart on changed by flipping the value of
debug. This has led to the same test being copied around. To reduce
the boiler plate code this change adds a new test helper which can
be used instead.

zaza/openstack/charm_tests/test_utils.py

@@ -254,6 +254,41 @@ class BaseCharmTest(unittest.TestCase):
         # TODO: Optimize with a block on a specific application until idle.
         model.block_until_all_units_idle()
 
+    def restart_on_changed_use_debug(self, config_file, services):
+        """Check restart happens on config change by flipping debug mode.
+
+        Change debug mode and assert that change propagates to the correct
+        file and that services are restarted as a result
+
+        :param config_file: Config file to check for settings
+        :type config_file: str
+        :param services: Services expected to be restarted when config_file is
+                         changed.
+        :type services: list
+        """
+        # Expected default and alternate values
+        current_value = model.get_application_config(
+            self.application_name)['debug']['value']
+        new_value = str(not bool(current_value)).title()
+        current_value = str(current_value).title()
+
+        set_default = {'debug': current_value}
+        set_alternate = {'debug': new_value}
+        default_entry = {'DEFAULT': {'debug': [current_value]}}
+        alternate_entry = {'DEFAULT': {'debug': [new_value]}}
+
+        # Make config change, check for service restarts
+        logging.info(
+            'Changing settings on {} to {}'.format(
+                self.application_name, set_alternate))
+        self.restart_on_changed(
+            config_file,
+            set_default,
+            set_alternate,
+            default_entry,
+            alternate_entry,
+            services)
+
     def restart_on_changed(self, config_file, default_config, alternate_config,
                            default_entry, alternate_entry, services,
                            pgrep_full=False):