Initial tiny attempt at (vectorable) counter metrics

tests/metrics/test_metric.py

@@ -0,0 +1,61 @@
+# -*- coding: utf-8 -*-
+# Copyright 2015 OpenMarket Ltd
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+from tests import unittest
+
+from synapse.metrics.metric import CounterMetric
+
+
+class CounterMetricTestCase(unittest.TestCase):
+
+    def test_scalar(self):
+        counter = CounterMetric("scalar")
+
+        self.assertEquals(counter.render(), [
+            "scalar 0",
+        ])
+
+        counter.inc()
+
+        self.assertEquals(counter.render(), [
+            "scalar 1",
+        ])
+
+        counter.inc()
+        counter.inc()
+
+        self.assertEquals(counter.render(), [
+            "scalar 3"
+        ])
+
+    def test_vector(self):
+        counter = CounterMetric("vector", keys=["method"])
+
+        # Empty counter doesn't yet know what values it has
+        self.assertEquals(counter.render(), [])
+
+        counter.inc("GET")
+
+        self.assertEquals(counter.render(), [
+            "vector{method=GET} 1",
+        ])
+
+        counter.inc("GET")
+        counter.inc("PUT")
+
+        self.assertEquals(counter.render(), [
+            "vector{method=GET} 2",
+            "vector{method=PUT} 1",
+        ])