Add tracking and formatting for last success in alerts

Relates to #2

minitor/main.py

@@ -123,6 +123,7 @@ class Monitor(object):
         self.alert_every = settings.get('alert_every')
 
         self.last_check = None
+        self.last_success = None
         self.total_failure_count = 0
         self.alert_count = 0
 
@@ -163,6 +164,7 @@ class Monitor(object):
         """Handles success tasks"""
         self.total_failure_count = 0
         self.alert_count = 0
+        self.last_success = datetime.now()
 
     def failure(self):
         """Handles failure tasks and possibly raises MinitorAlert"""
@@ -206,6 +208,12 @@ class Alert(object):
             args.append(arg.format(**kwargs))
         return args
 
+    def _format_datetime(self, dt):
+        """Formats a datetime for an alert"""
+        if dt is None:
+            return 'Never'
+        return dt.isoformat()
+
     def alert(self, monitor):
         """Calls the alert command for the provided monitor"""
         output, ex = call_output(
@@ -213,6 +221,7 @@ class Alert(object):
                 alert_count=monitor.alert_count,
                 monitor_name=monitor.name,
                 failure_count=monitor.total_failure_count,
+                last_success=self._format_datetime(monitor.last_success),
             ),
             shell=isinstance(self.command, str),
         )

tests/alert_test.py

@@ -1,3 +1,4 @@
+from datetime import datetime
 from unittest.mock import patch
 
 import pytest
@@ -23,18 +24,28 @@ class TestAlert(object):
                 'command': [
                     'echo', (
                         '{monitor_name} has failed {failure_count} time(s)!\n'
-                        'We have alerted {alert_count} time(s)'
+                        'We have alerted {alert_count} time(s)\n'
+                        'Last success was {last_success}'
                     )
                 ]
             }
         )
 
-    def test_simple_alert(self, monitor, echo_alert):
+    @pytest.mark.parametrize(
+        'last_success',
+        [
+            (None, 'Never'),
+            (datetime(2018, 4, 10), '2018-04-10T00:00:00')
+        ]
+    )
+    def test_simple_alert(self, monitor, echo_alert, last_success):
         monitor.total_failure_count = 1
         monitor.alert_count = 1
+        monitor.last_success = last_success[0]
         with patch.object(echo_alert.logger, 'error') as mock_error:
             echo_alert.alert(monitor)
         mock_error.assert_called_once_with(
             'Dummy Monitor has failed 1 time(s)!\n'
-            'We have alerted 1 time(s)'
+            'We have alerted 1 time(s)\n'
+            'Last success was ' + last_success[1]
         )