Refactor testutil/protobuf.go into scrape package

Renamed to clientprotobuf.go and added comments to indicate the
intended usage.

Signed-off-by: György Krajcsovits <gyorgy.krajcsovits@grafana.com>

scrape/clientprotobuf.go

@@ -11,17 +11,19 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-package testutil
+package scrape
 
 import (
 	"bytes"
 	"encoding/binary"
 
 	"github.com/gogo/protobuf/proto"
+	// Intentionally using client model to simulate client in tests.
 	dto "github.com/prometheus/client_model/go"
 )
 
-// Write a MetricFamily into a protobuf
+// Write a MetricFamily into a protobuf.
+// This function is intended for testing scraping by providing protobuf serialized input.
 func MetricFamilyToProtobuf(metricFamily *dto.MetricFamily) ([]byte, error) {
 	buffer := &bytes.Buffer{}
 	err := AddMetricFamilyToProtobuf(buffer, metricFamily)
@@ -31,7 +33,8 @@ func MetricFamilyToProtobuf(metricFamily *dto.MetricFamily) ([]byte, error) {
 	return buffer.Bytes(), nil
 }
 
-// Append a MetricFamily protobuf representation to a buffer
+// Append a MetricFamily protobuf representation to a buffer.
+// This function is intended for testing scraping by providing protobuf serialized input.
 func AddMetricFamilyToProtobuf(buffer *bytes.Buffer, metricFamily *dto.MetricFamily) error {
 	protoBuf, err := proto.Marshal(metricFamily)
 	if err != nil {

scrape/scrape_test.go

@@ -1766,7 +1766,7 @@ func TestScrapeLoop_HistogramBucketLimit(t *testing.T) {
 	require.NotEmpty(t, gathered)
 
 	histogramMetricFamily := gathered[0]
-	msg, err := testutil.MetricFamilyToProtobuf(histogramMetricFamily)
+	msg, err := MetricFamilyToProtobuf(histogramMetricFamily)
 	require.NoError(t, err)
 
 	now := time.Now()
@@ -1789,7 +1789,7 @@ func TestScrapeLoop_HistogramBucketLimit(t *testing.T) {
 	require.NotEmpty(t, gathered)
 
 	histogramMetricFamily = gathered[0]
-	msg, err = testutil.MetricFamilyToProtobuf(histogramMetricFamily)
+	msg, err = MetricFamilyToProtobuf(histogramMetricFamily)
 	require.NoError(t, err)
 
 	now = time.Now()