Print the URL into description

It helps to see what is the configured remote url and catch eventual
error in the set config.

Author: codebien

pkg/remotewrite/remotewrite.go

@@ -58,8 +58,8 @@ func New(params output.Params) (*Output, error) {
 	}, nil
 }
 
-func (*Output) Description() string {
-	return "Prometheus remote write"
+func (o *Output) Description() string {
+	return fmt.Sprintf("Prometheus remote write (%s)", o.config.URL.String)
 }
 
 func (o *Output) Start() error {

pkg/remotewrite/remotewrite_test.go

@@ -9,8 +9,20 @@ import (
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 	"go.k6.io/k6/metrics"
+	"gopkg.in/guregu/null.v3"
 )
 
+func TestOutputDescription(t *testing.T) {
+	t.Parallel()
+	o := Output{
+		config: Config{
+			URL: null.StringFrom("http://remote-url.fake"),
+		},
+	}
+	exp := "Prometheus remote write (http://remote-url.fake)"
+	assert.Equal(t, exp, o.Description())
+}
+
 func TestOutputConvertToPbSeries(t *testing.T) {
 	t.Parallel()