Add test for metrics prefix sanitization

Signed-off-by: Edwin Mackenzie-Owen <[email protected]>

Author: sysedwinistrator

stackdriver_exporter.go

@@ -304,7 +304,8 @@ func main() {
 
 	level.Info(logger).Log("msg", "Using Google Cloud Project IDs", "projectIDs", fmt.Sprintf("%v", projectIDs))
 
-	metricsTypePrefixes := parseMetricTypePrefixes()
+	inputPrefixes := strings.Split(*monitoringMetricsTypePrefixes, ",")
+	metricsTypePrefixes := parseMetricTypePrefixes(inputPrefixes)
 	metricExtraFilters := parseMetricExtraFilters()
 
 	if *metricsPath == *stackdriverMetricsPath {
@@ -354,9 +355,7 @@ func main() {
 	}
 }
 
-func parseMetricTypePrefixes() (metricTypePrefixes []string) {
-	inputPrefixes := strings.Split(*monitoringMetricsTypePrefixes, ",")
-
+func parseMetricTypePrefixes(inputPrefixes []string) (metricTypePrefixes []string) {
 	// only keep unique prefixes
 	uniqueKeys := make(map[string]bool)
 	uniquePrefixes := []string{}

stackdriver_exporter_test.go

@@ -0,0 +1,37 @@
+// Copyright 2020 The Prometheus Authors
+// 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.
+
+package main
+
+import "testing"
+import "reflect"
+
+func TestParseMetricTypePrefixes(t *testing.T) {
+	inputPrefixes := []string{
+		"redis.googleapis.com/stats/memory/usage",
+		"loadbalancing.googleapis.com/https/request_count",
+		"loadbalancing.googleapis.com",
+		"redis.googleapis.com/stats/memory/usage_ratio",
+		"redis.googleapis.com/stats/memory/usage_ratio",
+	}
+	expectedOutputPrefixes := []string{
+		"loadbalancing.googleapis.com",
+		"redis.googleapis.com/stats/memory/usage",
+	}
+
+	outputPrefixes := parseMetricTypePrefixes(inputPrefixes)
+
+	if !reflect.DeepEqual(outputPrefixes, expectedOutputPrefixes) {
+		t.Errorf("Metric type prefix sanitization did not produce expected output. Expected:\n%s\nGot:\n%s", expectedOutputPrefixes, outputPrefixes)
+	}
+}