Add tests for EncodeMetrics and DecodeMetrics

state/service_test.go

@@ -1,14 +1,31 @@
 package state
 
 import (
+	"bytes"
 	"encoding/json"
 	"expvar"
 	"testing"
 
+	"github.com/prometheus/client_golang/prometheus"
 	"github.com/spf13/viper"
 	"github.com/stretchr/testify/require"
 )
 
+type testCollector struct {
+	testA *prometheus.Desc
+	testB *prometheus.Desc
+}
+
+func (c *testCollector) Describe(ch chan<- *prometheus.Desc) {
+	ch <- c.testA
+	ch <- c.testB
+}
+
+func (c *testCollector) Collect(ch chan<- prometheus.Metric) {
+	ch <- prometheus.MustNewConstMetric(c.testA, prometheus.GaugeValue, 1, "label_1")
+	ch <- prometheus.MustNewConstMetric(c.testB, prometheus.GaugeValue, 2, "label_2")
+}
+
 func TestEncodeVariables(t *testing.T) {
 	dump := make(map[string]interface{})
 
@@ -47,3 +64,55 @@ func TestEncodeConfig(t *testing.T) {
 	require.Contains(t, dump, "test2")
 	require.Equal(t, dump["test2"], "test2")
 }
+
+func TestEncodeAndDecodeMetrics(t *testing.T) {
+	registry := prometheus.NewRegistry()
+
+	collector := &testCollector{
+		testA: prometheus.NewDesc("test1", "test1", []string{"test1"}, prometheus.Labels{"label_1": "test1"}),
+		testB: prometheus.NewDesc("test2", "test2", []string{"test2"}, prometheus.Labels{"label_2": "test2"}),
+	}
+
+	require.NoError(t, registry.Register(collector))
+
+	gather, err := registry.Gather()
+	require.NoError(t, err)
+
+	res, err := EncodeMetrics(registry)
+	require.NoError(t, err)
+
+	metrics, err := DecodeMetrics(res)
+	require.NoError(t, err)
+
+	require.Len(t, metrics, len(gather))
+
+	{ // Check that JSON encoded metrics are equal:
+		expect := new(bytes.Buffer)
+		actual := new(bytes.Buffer)
+
+		require.NoError(t, json.NewEncoder(expect).Encode(gather))
+		require.NoError(t, json.NewEncoder(actual).Encode(metrics))
+
+		require.Equal(t, expect.Bytes(), actual.Bytes())
+	}
+
+	{ // Deep comparison of metrics:
+		for i := range metrics {
+			require.Equal(t, gather[i].Help, metrics[i].Help)
+			require.Equal(t, gather[i].Name, metrics[i].Name)
+			require.Equal(t, gather[i].Type, metrics[i].Type)
+
+			require.Len(t, metrics[i].Metric, len(gather[i].Metric))
+
+			for j := range metrics[i].Metric {
+				require.Equal(t, gather[i].Metric[j].Gauge, metrics[i].Metric[j].Gauge)
+				require.Len(t, metrics[i].Metric[j].Label, len(gather[i].Metric[j].Label))
+
+				for k := range metrics[i].Metric[j].Label {
+					require.Equal(t, gather[i].Metric[j].Label[k].Name, metrics[i].Metric[j].Label[k].Name)
+					require.Equal(t, gather[i].Metric[j].Label[k].Value, metrics[i].Metric[j].Label[k].Value)
+				}
+			}
+		}
+	}
+}