fix bad Gauge test (#975)

metrics/cloudwatch/cloudwatch.go

@@ -175,16 +175,16 @@ func (cw *CloudWatch) Send() error {
 	})
 
 	cw.gauges.Reset().Walk(func(name string, lvs lv.LabelValues, values []float64) bool {
+		if len(values) == 0 {
+			return true
+		}
+
 		datum := &cloudwatch.MetricDatum{
 			MetricName: aws.String(name),
 			Dimensions: makeDimensions(lvs...),
 			Timestamp:  aws.Time(now),
 		}
 
-		if len(values) == 0 {
-			return true
-		}
-
 		// CloudWatch Put Metrics API (https://docs.aws.amazon.com/AmazonCloudWatch/latest/APIReference/API_MetricDatum.html)
 		// expects batch of unique values including the array of corresponding counts
 		valuesCounter := make(map[float64]int)

metrics/cloudwatch/cloudwatch_test.go

@@ -164,9 +164,9 @@ func TestGauge(t *testing.T) {
 			t.Fatal(err)
 		}
 		svc.mtx.RLock()
+		defer svc.mtx.RUnlock()
 		res := svc.valuesReceived[name]
 		delete(svc.valuesReceived, name)
-		defer svc.mtx.RUnlock()
 		return res
 	}
 

metrics/teststat/teststat.go

@@ -7,6 +7,7 @@ import (
 	"math"
 	"math/rand"
 	"reflect"
+	"sort"
 	"strings"
 
 	"github.com/go-kit/kit/metrics"
@@ -53,11 +54,24 @@ func TestGauge(gauge metrics.Gauge, value func() []float64) error {
 	for i := 0; i < n; i++ {
 		f := float64(a[i])
 		gauge.Add(f)
-		want[len(want)-1] += f
+		want = append(want, want[len(want)-1]+f)
 	}
 
-	if have := value(); reflect.DeepEqual(want, have) {
-		return fmt.Errorf("want %f, have %f", want, have)
+	have := value()
+
+	switch len(have) {
+	case 0:
+		return fmt.Errorf("got 0 values")
+	case 1: // provider doesn't support multi value
+		if have[0] != want[len(want)-1] {
+			return fmt.Errorf("want %f, have %f", want, have)
+		}
+	default: // provider support multi value gauges
+		sort.Float64s(want)
+		sort.Float64s(have)
+		if !reflect.DeepEqual(want, have) {
+			return fmt.Errorf("want %f, have %f", want, have)
+		}
 	}
 
 	return nil