Fixes prometheus start metric

test/test_metricqueue.py

@@ -2,7 +2,7 @@ import time
 import unittest
 
 from mock import Mock
-from trollius import coroutine, Return, get_event_loop
+from trollius import coroutine, Return, get_event_loop, From
 
 from util.metrics.metricqueue import duration_collector_async
 
@@ -25,6 +25,10 @@ def duration_decorated():
 def duration_decorated_error():
     raise NonReturn("not a Return error")
 
+@coroutine
+def calls_decorated():
+  yield From(duration_decorated())
+
 
 class DurationDecoratorTestCase(unittest.TestCase):
   def __init__(self, *args, **kwargs):
@@ -44,7 +48,15 @@ class DurationDecoratorTestCase(unittest.TestCase):
     with self.assertRaises(NonReturn):
       self.loop.run_until_complete(duration_decorated_error())
     assert not mock_histogram.Observe.called
-
+    
+  def test_duration_decorator_caller(self):
+    mock_histogram.reset_mock()
+    
+    self.loop.run_until_complete(calls_decorated())
+    assert mock_histogram.Observe.called
+    assert 1 - mock_histogram.Observe.call_args[0][0] < 1  # duration should be close to 1s
+    assert mock_histogram.Observe.call_args[1]["labelvalues"] == ["testlabel"]
+    
 
 if __name__ == '__main__':
   unittest.main()