From 5d3b089f0c32701cd05eee546796d377b803574a Mon Sep 17 00:00:00 2001
From: Frederic Branczyk <fbranczyk@gmail.com>
Date: Tue, 3 Jul 2018 13:25:00 +0200
Subject: [PATCH 1/7] Add testutils package

Signed-off-by: Frederic Branczyk <fbranczyk@gmail.com>
---
 testutils/testutils.go      | 182 ++++++++++++++++++++++++++++++++++++
 testutils/testutils_test.go | 100 ++++++++++++++++++++
 2 files changed, 282 insertions(+)
 create mode 100644 testutils/testutils.go
 create mode 100644 testutils/testutils_test.go

diff --git a/testutils/testutils.go b/testutils/testutils.go
new file mode 100644
index 0000000..c6da37b
--- /dev/null
+++ b/testutils/testutils.go
@@ -0,0 +1,182 @@
+/*
+Copyright 2018 The Prometheus Authors All rights reserved.
+
+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 testutils
+
+import (
+	"bytes"
+	"fmt"
+	"reflect"
+	"sort"
+	"strings"
+
+	"github.com/prometheus/client_golang/prometheus"
+	dto "github.com/prometheus/client_model/go"
+	"github.com/prometheus/common/expfmt"
+)
+
+// GatherAndCompare retrieves all metrics exposed by a collector and compares it
+// to an expected output in the Prometheus text exposition format.
+// metricNames allows only comparing the given metrics. All are compared if it's nil.
+func GatherAndCompare(c prometheus.Collector, expected string, metricNames ...string) error {
+	expected = removeUnusedWhitespace(expected)
+
+	reg := prometheus.NewPedanticRegistry()
+	if err := reg.Register(c); err != nil {
+		return fmt.Errorf("registering collector failed: %s", err)
+	}
+	metrics, err := reg.Gather()
+	if err != nil {
+		return fmt.Errorf("gathering metrics failed: %s", err)
+	}
+	if metricNames != nil {
+		metrics = filterMetrics(metrics, metricNames)
+	}
+	var tp expfmt.TextParser
+	expectedMetrics, err := tp.TextToMetricFamilies(bytes.NewReader([]byte(expected)))
+	if err != nil {
+		return fmt.Errorf("parsing expected metrics failed: %s", err)
+	}
+
+	if !reflect.DeepEqual(metrics, normalizeMetricFamilies(expectedMetrics)) {
+		// Encode the gathered output to the readbale text format for comparison.
+		var buf1 bytes.Buffer
+		enc := expfmt.NewEncoder(&buf1, expfmt.FmtText)
+		for _, mf := range metrics {
+			if err := enc.Encode(mf); err != nil {
+				return fmt.Errorf("encoding result failed: %s", err)
+			}
+		}
+		// Encode normalized expected metrics again to generate them in the same ordering
+		// the registry does to spot differences more easily.
+		var buf2 bytes.Buffer
+		enc = expfmt.NewEncoder(&buf2, expfmt.FmtText)
+		for _, mf := range normalizeMetricFamilies(expectedMetrics) {
+			if err := enc.Encode(mf); err != nil {
+				return fmt.Errorf("encoding result failed: %s", err)
+			}
+		}
+
+		return fmt.Errorf(`
+metric output does not match expectation; want:
+
+%s
+
+got:
+
+%s
+`, buf2.String(), buf1.String())
+	}
+	return nil
+}
+
+func filterMetrics(metrics []*dto.MetricFamily, names []string) []*dto.MetricFamily {
+	var filtered []*dto.MetricFamily
+	for _, m := range metrics {
+		drop := true
+		for _, name := range names {
+			if m.GetName() == name {
+				drop = false
+				break
+			}
+		}
+		if !drop {
+			filtered = append(filtered, m)
+		}
+	}
+	return filtered
+}
+
+func removeUnusedWhitespace(s string) string {
+	var (
+		trimmedLine  string
+		trimmedLines []string
+		lines        = strings.Split(s, "\n")
+	)
+
+	for _, l := range lines {
+		trimmedLine = strings.TrimSpace(l)
+
+		if len(trimmedLine) > 0 {
+			trimmedLines = append(trimmedLines, trimmedLine)
+		}
+	}
+
+	// The Prometheus metrics representation parser expects an empty line at the
+	// end otherwise fails with an unexpected EOF error.
+	return strings.Join(trimmedLines, "\n") + "\n"
+}
+
+// The below sorting code is copied form the Prometheus client library modulo the added
+// label pair sorting.
+// https://github.com/prometheus/client_golang/blob/ea6e1db4cb8127eeb0b6954f7320363e5451820f/prometheus/registry.go#L642-L684
+
+// metricSorter is a sortable slice of *dto.Metric.
+type metricSorter []*dto.Metric
+
+func (s metricSorter) Len() int {
+	return len(s)
+}
+
+func (s metricSorter) Swap(i, j int) {
+	s[i], s[j] = s[j], s[i]
+}
+
+func (s metricSorter) Less(i, j int) bool {
+	sort.Sort(prometheus.LabelPairSorter(s[i].Label))
+	sort.Sort(prometheus.LabelPairSorter(s[j].Label))
+
+	if len(s[i].Label) != len(s[j].Label) {
+		return len(s[i].Label) < len(s[j].Label)
+	}
+
+	for n, lp := range s[i].Label {
+		vi := lp.GetValue()
+		vj := s[j].Label[n].GetValue()
+		if vi != vj {
+			return vi < vj
+		}
+	}
+
+	if s[i].TimestampMs == nil {
+		return false
+	}
+	if s[j].TimestampMs == nil {
+		return true
+	}
+	return s[i].GetTimestampMs() < s[j].GetTimestampMs()
+}
+
+// normalizeMetricFamilies returns a MetricFamily slice with empty
+// MetricFamilies pruned and the remaining MetricFamilies sorted by name within
+// the slice, with the contained Metrics sorted within each MetricFamily.
+func normalizeMetricFamilies(metricFamiliesByName map[string]*dto.MetricFamily) []*dto.MetricFamily {
+	for _, mf := range metricFamiliesByName {
+		sort.Sort(metricSorter(mf.Metric))
+	}
+	names := make([]string, 0, len(metricFamiliesByName))
+	for name, mf := range metricFamiliesByName {
+		if len(mf.Metric) > 0 {
+			names = append(names, name)
+		}
+	}
+	sort.Strings(names)
+	result := make([]*dto.MetricFamily, 0, len(names))
+	for _, name := range names {
+		result = append(result, metricFamiliesByName[name])
+	}
+	return result
+}
diff --git a/testutils/testutils_test.go b/testutils/testutils_test.go
new file mode 100644
index 0000000..96ad971
--- /dev/null
+++ b/testutils/testutils_test.go
@@ -0,0 +1,100 @@
+package testutils
+
+import (
+	"testing"
+
+	"github.com/prometheus/client_golang/prometheus"
+)
+
+func TestGatherAndCompare(t *testing.T) {
+	const metadata = `
+		# HELP some_total A value that represents a counter.
+		# TYPE some_total counter
+	`
+
+	c := prometheus.NewCounter(prometheus.CounterOpts{
+		Name: "some_total",
+		Help: "A value that represents a counter.",
+		ConstLabels: prometheus.Labels{
+			"label1": "value1",
+		},
+	})
+	c.Inc()
+
+	expected := `
+		some_total{label1="value1"} 1
+	`
+
+	if err := GatherAndCompare(c, metadata+expected, "some_total"); err != nil {
+		t.Errorf("unexpected collecting result:\n%s", err)
+	}
+}
+
+func TestNoMetricFilter(t *testing.T) {
+	const metadata = `
+		# HELP some_total A value that represents a counter.
+		# TYPE some_total counter
+	`
+
+	c := prometheus.NewCounter(prometheus.CounterOpts{
+		Name: "some_total",
+		Help: "A value that represents a counter.",
+		ConstLabels: prometheus.Labels{
+			"label1": "value1",
+		},
+	})
+	c.Inc()
+
+	expected := `
+		some_total{label1="value1"} 1
+	`
+
+	if err := GatherAndCompare(c, metadata+expected); err != nil {
+		t.Errorf("unexpected collecting result:\n%s", err)
+	}
+}
+
+func TestMetricNotFound(t *testing.T) {
+	const metadata = `
+		# HELP some_other_metric A value that represents a counter.
+		# TYPE some_other_metric counter
+	`
+
+	c := prometheus.NewCounter(prometheus.CounterOpts{
+		Name: "some_total",
+		Help: "A value that represents a counter.",
+		ConstLabels: prometheus.Labels{
+			"label1": "value1",
+		},
+	})
+	c.Inc()
+
+	expected := `
+		some_other_metric{label1="value1"} 1
+	`
+
+	expectedError := `
+metric output does not match expectation; want:
+
+# HELP some_other_metric A value that represents a counter.
+# TYPE some_other_metric counter
+some_other_metric{label1="value1"} 1
+
+
+got:
+
+# HELP some_total A value that represents a counter.
+# TYPE some_total counter
+some_total{label1="value1"} 1
+
+`
+
+	err := GatherAndCompare(c, metadata+expected)
+	if err == nil {
+		t.Error("Expected error, got no error.")
+	}
+
+	if err.Error() != expectedError {
+		t.Errorf("Expected\n%#+v\nGot:\n%#+v\n", expectedError, err.Error())
+	}
+}

From fc4994c93c739aabbf873535ec1951be4aa839bc Mon Sep 17 00:00:00 2001
From: beorn7 <beorn@soundcloud.com>
Date: Wed, 22 Aug 2018 23:54:26 +0200
Subject: [PATCH 2/7] Remove removeUnusedWhitespace

It wasn't needed, as is now proven by the tests

Signed-off-by: beorn7 <beorn@soundcloud.com>
---
 testutils/testutils.go      | 23 -----------------------
 testutils/testutils_test.go |  3 ++-
 2 files changed, 2 insertions(+), 24 deletions(-)

diff --git a/testutils/testutils.go b/testutils/testutils.go
index c6da37b..c732a03 100644
--- a/testutils/testutils.go
+++ b/testutils/testutils.go
@@ -21,7 +21,6 @@ import (
 	"fmt"
 	"reflect"
 	"sort"
-	"strings"
 
 	"github.com/prometheus/client_golang/prometheus"
 	dto "github.com/prometheus/client_model/go"
@@ -32,8 +31,6 @@ import (
 // to an expected output in the Prometheus text exposition format.
 // metricNames allows only comparing the given metrics. All are compared if it's nil.
 func GatherAndCompare(c prometheus.Collector, expected string, metricNames ...string) error {
-	expected = removeUnusedWhitespace(expected)
-
 	reg := prometheus.NewPedanticRegistry()
 	if err := reg.Register(c); err != nil {
 		return fmt.Errorf("registering collector failed: %s", err)
@@ -100,26 +97,6 @@ func filterMetrics(metrics []*dto.MetricFamily, names []string) []*dto.MetricFam
 	return filtered
 }
 
-func removeUnusedWhitespace(s string) string {
-	var (
-		trimmedLine  string
-		trimmedLines []string
-		lines        = strings.Split(s, "\n")
-	)
-
-	for _, l := range lines {
-		trimmedLine = strings.TrimSpace(l)
-
-		if len(trimmedLine) > 0 {
-			trimmedLines = append(trimmedLines, trimmedLine)
-		}
-	}
-
-	// The Prometheus metrics representation parser expects an empty line at the
-	// end otherwise fails with an unexpected EOF error.
-	return strings.Join(trimmedLines, "\n") + "\n"
-}
-
 // The below sorting code is copied form the Prometheus client library modulo the added
 // label pair sorting.
 // https://github.com/prometheus/client_golang/blob/ea6e1db4cb8127eeb0b6954f7320363e5451820f/prometheus/registry.go#L642-L684
diff --git a/testutils/testutils_test.go b/testutils/testutils_test.go
index 96ad971..54bdf8e 100644
--- a/testutils/testutils_test.go
+++ b/testutils/testutils_test.go
@@ -22,7 +22,8 @@ func TestGatherAndCompare(t *testing.T) {
 	c.Inc()
 
 	expected := `
-		some_total{label1="value1"} 1
+
+		some_total{ label1 = "value1" } 1
 	`
 
 	if err := GatherAndCompare(c, metadata+expected, "some_total"); err != nil {

From df0210c26c04b26e86ca119eb2fe60f89d8f54f3 Mon Sep 17 00:00:00 2001
From: beorn7 <beorn@soundcloud.com>
Date: Wed, 22 Aug 2018 23:57:08 +0200
Subject: [PATCH 3/7] Rename testutils to testutil and move below prometheus
 dir

`testutil` is more in line with stdlib naming conventions.

The package should be below `prometheus` as it only provides utils to
test exposition code, not to test HTTP client code.

Signed-off-by: beorn7 <beorn@soundcloud.com>
---
 testutils/testutils.go => prometheus/testutil/testutil.go       | 2 +-
 .../testutils_test.go => prometheus/testutil/testutil_test.go   | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)
 rename testutils/testutils.go => prometheus/testutil/testutil.go (99%)
 rename testutils/testutils_test.go => prometheus/testutil/testutil_test.go (99%)

diff --git a/testutils/testutils.go b/prometheus/testutil/testutil.go
similarity index 99%
rename from testutils/testutils.go
rename to prometheus/testutil/testutil.go
index c732a03..562009c 100644
--- a/testutils/testutils.go
+++ b/prometheus/testutil/testutil.go
@@ -14,7 +14,7 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-package testutils
+package testutil
 
 import (
 	"bytes"
diff --git a/testutils/testutils_test.go b/prometheus/testutil/testutil_test.go
similarity index 99%
rename from testutils/testutils_test.go
rename to prometheus/testutil/testutil_test.go
index 54bdf8e..773b94c 100644
--- a/testutils/testutils_test.go
+++ b/prometheus/testutil/testutil_test.go
@@ -1,4 +1,4 @@
-package testutils
+package testutil
 
 import (
 	"testing"

From e60f998e9bf9a38e4e9be5bedfa86bd367cee3fa Mon Sep 17 00:00:00 2001
From: beorn7 <beorn@soundcloud.com>
Date: Wed, 22 Aug 2018 23:59:40 +0200
Subject: [PATCH 4/7] Make license headers consistent

Signed-off-by: beorn7 <beorn@soundcloud.com>
---
 prometheus/testutil/testutil.go      | 27 ++++++++++++---------------
 prometheus/testutil/testutil_test.go | 13 +++++++++++++
 2 files changed, 25 insertions(+), 15 deletions(-)

diff --git a/prometheus/testutil/testutil.go b/prometheus/testutil/testutil.go
index 562009c..3acb8ef 100644
--- a/prometheus/testutil/testutil.go
+++ b/prometheus/testutil/testutil.go
@@ -1,18 +1,15 @@
-/*
-Copyright 2018 The Prometheus Authors All rights reserved.
-
-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.
-*/
+// Copyright 2018 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 testutil
 
diff --git a/prometheus/testutil/testutil_test.go b/prometheus/testutil/testutil_test.go
index 773b94c..a05eda7 100644
--- a/prometheus/testutil/testutil_test.go
+++ b/prometheus/testutil/testutil_test.go
@@ -1,3 +1,16 @@
+// Copyright 2018 he 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 testutil
 
 import (

From 154f28a3168edf383139f13aff9fd3df3d7e858b Mon Sep 17 00:00:00 2001
From: beorn7 <beorn@soundcloud.com>
Date: Thu, 23 Aug 2018 00:05:02 +0200
Subject: [PATCH 5/7] Fix import grouping

Signed-off-by: beorn7 <beorn@soundcloud.com>
---
 prometheus/testutil/testutil.go | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/prometheus/testutil/testutil.go b/prometheus/testutil/testutil.go
index 3acb8ef..6145833 100644
--- a/prometheus/testutil/testutil.go
+++ b/prometheus/testutil/testutil.go
@@ -19,9 +19,11 @@ import (
 	"reflect"
 	"sort"
 
-	"github.com/prometheus/client_golang/prometheus"
-	dto "github.com/prometheus/client_model/go"
 	"github.com/prometheus/common/expfmt"
+
+	dto "github.com/prometheus/client_model/go"
+
+	"github.com/prometheus/client_golang/prometheus"
 )
 
 // GatherAndCompare retrieves all metrics exposed by a collector and compares it

From 5ba0993f6f91a7be093f0460572ee88d435cc94c Mon Sep 17 00:00:00 2001
From: beorn7 <beorn@soundcloud.com>
Date: Thu, 23 Aug 2018 00:21:38 +0200
Subject: [PATCH 6/7] Improved interface

- Expected text format is now read from an io.Reader.
- Metrics are gathered from a Gatherer.
- Added a convenience wrapper to collect from a Collector.

Signed-off-by: beorn7 <beorn@soundcloud.com>
---
 prometheus/testutil/testutil.go      | 29 ++++++++++++++++------------
 prometheus/testutil/testutil_test.go | 11 ++++++-----
 2 files changed, 23 insertions(+), 17 deletions(-)

diff --git a/prometheus/testutil/testutil.go b/prometheus/testutil/testutil.go
index 6145833..5d731ae 100644
--- a/prometheus/testutil/testutil.go
+++ b/prometheus/testutil/testutil.go
@@ -16,6 +16,7 @@ package testutil
 import (
 	"bytes"
 	"fmt"
+	"io"
 	"reflect"
 	"sort"
 
@@ -26,15 +27,23 @@ import (
 	"github.com/prometheus/client_golang/prometheus"
 )
 
-// GatherAndCompare retrieves all metrics exposed by a collector and compares it
-// to an expected output in the Prometheus text exposition format.
-// metricNames allows only comparing the given metrics. All are compared if it's nil.
-func GatherAndCompare(c prometheus.Collector, expected string, metricNames ...string) error {
+// CollectAndCompare registers the provided Collector with a newly created
+// pedantic Registry. It then does the same as GatherAndCompare, gathering the
+// metrics from the pedantic Registry.
+func CollectAndCompare(c prometheus.Collector, expected io.Reader, metricNames ...string) error {
 	reg := prometheus.NewPedanticRegistry()
 	if err := reg.Register(c); err != nil {
 		return fmt.Errorf("registering collector failed: %s", err)
 	}
-	metrics, err := reg.Gather()
+	return GatherAndCompare(reg, expected, metricNames...)
+}
+
+// GatherAndCompare gathers all metrics from the provided Gatherer and compares
+// it to an expected output read from the provided Reader in the Prometheus text
+// exposition format. If any metricNames are provided, only metrics with those
+// names are compared.
+func GatherAndCompare(g prometheus.Gatherer, expected io.Reader, metricNames ...string) error {
+	metrics, err := g.Gather()
 	if err != nil {
 		return fmt.Errorf("gathering metrics failed: %s", err)
 	}
@@ -42,13 +51,13 @@ func GatherAndCompare(c prometheus.Collector, expected string, metricNames ...st
 		metrics = filterMetrics(metrics, metricNames)
 	}
 	var tp expfmt.TextParser
-	expectedMetrics, err := tp.TextToMetricFamilies(bytes.NewReader([]byte(expected)))
+	expectedMetrics, err := tp.TextToMetricFamilies(expected)
 	if err != nil {
 		return fmt.Errorf("parsing expected metrics failed: %s", err)
 	}
 
 	if !reflect.DeepEqual(metrics, normalizeMetricFamilies(expectedMetrics)) {
-		// Encode the gathered output to the readbale text format for comparison.
+		// Encode the gathered output to the readable text format for comparison.
 		var buf1 bytes.Buffer
 		enc := expfmt.NewEncoder(&buf1, expfmt.FmtText)
 		for _, mf := range metrics {
@@ -82,16 +91,12 @@ got:
 func filterMetrics(metrics []*dto.MetricFamily, names []string) []*dto.MetricFamily {
 	var filtered []*dto.MetricFamily
 	for _, m := range metrics {
-		drop := true
 		for _, name := range names {
 			if m.GetName() == name {
-				drop = false
+				filtered = append(filtered, m)
 				break
 			}
 		}
-		if !drop {
-			filtered = append(filtered, m)
-		}
 	}
 	return filtered
 }
diff --git a/prometheus/testutil/testutil_test.go b/prometheus/testutil/testutil_test.go
index a05eda7..b4e7b01 100644
--- a/prometheus/testutil/testutil_test.go
+++ b/prometheus/testutil/testutil_test.go
@@ -1,4 +1,4 @@
-// Copyright 2018 he Prometheus Authors
+// Copyright 2018 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
@@ -14,12 +14,13 @@
 package testutil
 
 import (
+	"strings"
 	"testing"
 
 	"github.com/prometheus/client_golang/prometheus"
 )
 
-func TestGatherAndCompare(t *testing.T) {
+func TestCollectAndCompare(t *testing.T) {
 	const metadata = `
 		# HELP some_total A value that represents a counter.
 		# TYPE some_total counter
@@ -39,7 +40,7 @@ func TestGatherAndCompare(t *testing.T) {
 		some_total{ label1 = "value1" } 1
 	`
 
-	if err := GatherAndCompare(c, metadata+expected, "some_total"); err != nil {
+	if err := CollectAndCompare(c, strings.NewReader(metadata+expected), "some_total"); err != nil {
 		t.Errorf("unexpected collecting result:\n%s", err)
 	}
 }
@@ -63,7 +64,7 @@ func TestNoMetricFilter(t *testing.T) {
 		some_total{label1="value1"} 1
 	`
 
-	if err := GatherAndCompare(c, metadata+expected); err != nil {
+	if err := CollectAndCompare(c, strings.NewReader(metadata+expected)); err != nil {
 		t.Errorf("unexpected collecting result:\n%s", err)
 	}
 }
@@ -103,7 +104,7 @@ some_total{label1="value1"} 1
 
 `
 
-	err := GatherAndCompare(c, metadata+expected)
+	err := CollectAndCompare(c, strings.NewReader(metadata+expected))
 	if err == nil {
 		t.Error("Expected error, got no error.")
 	}

From 7be86f93c1d6fd608a6d29493fbdacc630f10e13 Mon Sep 17 00:00:00 2001
From: beorn7 <beorn@soundcloud.com>
Date: Sun, 2 Sep 2018 23:36:34 +0200
Subject: [PATCH 7/7] Create an internal package

This is for types we don't want to export but which are used in
different packages within client_golang.

Currently, that's only NormalizeMetricFamilies (used in the prometheus
package and in the testutil package). More to be added as needed.

Signed-off-by: beorn7 <beorn@soundcloud.com>
---
 prometheus/internal/metric.go   | 85 +++++++++++++++++++++++++++++++++
 prometheus/registry.go          | 71 ++-------------------------
 prometheus/testutil/testutil.go | 67 ++------------------------
 3 files changed, 92 insertions(+), 131 deletions(-)
 create mode 100644 prometheus/internal/metric.go

diff --git a/prometheus/internal/metric.go b/prometheus/internal/metric.go
new file mode 100644
index 0000000..351c26e
--- /dev/null
+++ b/prometheus/internal/metric.go
@@ -0,0 +1,85 @@
+// Copyright 2018 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 internal
+
+import (
+	"sort"
+
+	dto "github.com/prometheus/client_model/go"
+)
+
+// metricSorter is a sortable slice of *dto.Metric.
+type metricSorter []*dto.Metric
+
+func (s metricSorter) Len() int {
+	return len(s)
+}
+
+func (s metricSorter) Swap(i, j int) {
+	s[i], s[j] = s[j], s[i]
+}
+
+func (s metricSorter) Less(i, j int) bool {
+	if len(s[i].Label) != len(s[j].Label) {
+		// This should not happen. The metrics are
+		// inconsistent. However, we have to deal with the fact, as
+		// people might use custom collectors or metric family injection
+		// to create inconsistent metrics. So let's simply compare the
+		// number of labels in this case. That will still yield
+		// reproducible sorting.
+		return len(s[i].Label) < len(s[j].Label)
+	}
+	for n, lp := range s[i].Label {
+		vi := lp.GetValue()
+		vj := s[j].Label[n].GetValue()
+		if vi != vj {
+			return vi < vj
+		}
+	}
+
+	// We should never arrive here. Multiple metrics with the same
+	// label set in the same scrape will lead to undefined ingestion
+	// behavior. However, as above, we have to provide stable sorting
+	// here, even for inconsistent metrics. So sort equal metrics
+	// by their timestamp, with missing timestamps (implying "now")
+	// coming last.
+	if s[i].TimestampMs == nil {
+		return false
+	}
+	if s[j].TimestampMs == nil {
+		return true
+	}
+	return s[i].GetTimestampMs() < s[j].GetTimestampMs()
+}
+
+// NormalizeMetricFamilies returns a MetricFamily slice with empty
+// MetricFamilies pruned and the remaining MetricFamilies sorted by name within
+// the slice, with the contained Metrics sorted within each MetricFamily.
+func NormalizeMetricFamilies(metricFamiliesByName map[string]*dto.MetricFamily) []*dto.MetricFamily {
+	for _, mf := range metricFamiliesByName {
+		sort.Sort(metricSorter(mf.Metric))
+	}
+	names := make([]string, 0, len(metricFamiliesByName))
+	for name, mf := range metricFamiliesByName {
+		if len(mf.Metric) > 0 {
+			names = append(names, name)
+		}
+	}
+	sort.Strings(names)
+	result := make([]*dto.MetricFamily, 0, len(names))
+	for _, name := range names {
+		result = append(result, metricFamiliesByName[name])
+	}
+	return result
+}
diff --git a/prometheus/registry.go b/prometheus/registry.go
index 896838f..79c3dd6 100644
--- a/prometheus/registry.go
+++ b/prometheus/registry.go
@@ -26,6 +26,8 @@ import (
 	"github.com/golang/protobuf/proto"
 
 	dto "github.com/prometheus/client_model/go"
+
+	"github.com/prometheus/client_golang/prometheus/internal"
 )
 
 const (
@@ -527,7 +529,7 @@ func (r *Registry) Gather() ([]*dto.MetricFamily, error) {
 			break
 		}
 	}
-	return normalizeMetricFamilies(metricFamiliesByName), errs.MaybeUnwrap()
+	return internal.NormalizeMetricFamilies(metricFamiliesByName), errs.MaybeUnwrap()
 }
 
 // processMetric is an internal helper method only used by the Gather method.
@@ -707,72 +709,7 @@ func (gs Gatherers) Gather() ([]*dto.MetricFamily, error) {
 			}
 		}
 	}
-	return normalizeMetricFamilies(metricFamiliesByName), errs.MaybeUnwrap()
-}
-
-// metricSorter is a sortable slice of *dto.Metric.
-type metricSorter []*dto.Metric
-
-func (s metricSorter) Len() int {
-	return len(s)
-}
-
-func (s metricSorter) Swap(i, j int) {
-	s[i], s[j] = s[j], s[i]
-}
-
-func (s metricSorter) Less(i, j int) bool {
-	if len(s[i].Label) != len(s[j].Label) {
-		// This should not happen. The metrics are
-		// inconsistent. However, we have to deal with the fact, as
-		// people might use custom collectors or metric family injection
-		// to create inconsistent metrics. So let's simply compare the
-		// number of labels in this case. That will still yield
-		// reproducible sorting.
-		return len(s[i].Label) < len(s[j].Label)
-	}
-	for n, lp := range s[i].Label {
-		vi := lp.GetValue()
-		vj := s[j].Label[n].GetValue()
-		if vi != vj {
-			return vi < vj
-		}
-	}
-
-	// We should never arrive here. Multiple metrics with the same
-	// label set in the same scrape will lead to undefined ingestion
-	// behavior. However, as above, we have to provide stable sorting
-	// here, even for inconsistent metrics. So sort equal metrics
-	// by their timestamp, with missing timestamps (implying "now")
-	// coming last.
-	if s[i].TimestampMs == nil {
-		return false
-	}
-	if s[j].TimestampMs == nil {
-		return true
-	}
-	return s[i].GetTimestampMs() < s[j].GetTimestampMs()
-}
-
-// normalizeMetricFamilies returns a MetricFamily slice with empty
-// MetricFamilies pruned and the remaining MetricFamilies sorted by name within
-// the slice, with the contained Metrics sorted within each MetricFamily.
-func normalizeMetricFamilies(metricFamiliesByName map[string]*dto.MetricFamily) []*dto.MetricFamily {
-	for _, mf := range metricFamiliesByName {
-		sort.Sort(metricSorter(mf.Metric))
-	}
-	names := make([]string, 0, len(metricFamiliesByName))
-	for name, mf := range metricFamiliesByName {
-		if len(mf.Metric) > 0 {
-			names = append(names, name)
-		}
-	}
-	sort.Strings(names)
-	result := make([]*dto.MetricFamily, 0, len(names))
-	for _, name := range names {
-		result = append(result, metricFamiliesByName[name])
-	}
-	return result
+	return internal.NormalizeMetricFamilies(metricFamiliesByName), errs.MaybeUnwrap()
 }
 
 // checkSuffixCollisions checks for collisions with the “magic” suffixes the
diff --git a/prometheus/testutil/testutil.go b/prometheus/testutil/testutil.go
index 5d731ae..dc2ce22 100644
--- a/prometheus/testutil/testutil.go
+++ b/prometheus/testutil/testutil.go
@@ -18,13 +18,13 @@ import (
 	"fmt"
 	"io"
 	"reflect"
-	"sort"
 
 	"github.com/prometheus/common/expfmt"
 
 	dto "github.com/prometheus/client_model/go"
 
 	"github.com/prometheus/client_golang/prometheus"
+	"github.com/prometheus/client_golang/prometheus/internal"
 )
 
 // CollectAndCompare registers the provided Collector with a newly created
@@ -56,7 +56,7 @@ func GatherAndCompare(g prometheus.Gatherer, expected io.Reader, metricNames ...
 		return fmt.Errorf("parsing expected metrics failed: %s", err)
 	}
 
-	if !reflect.DeepEqual(metrics, normalizeMetricFamilies(expectedMetrics)) {
+	if !reflect.DeepEqual(metrics, internal.NormalizeMetricFamilies(expectedMetrics)) {
 		// Encode the gathered output to the readable text format for comparison.
 		var buf1 bytes.Buffer
 		enc := expfmt.NewEncoder(&buf1, expfmt.FmtText)
@@ -69,7 +69,7 @@ func GatherAndCompare(g prometheus.Gatherer, expected io.Reader, metricNames ...
 		// the registry does to spot differences more easily.
 		var buf2 bytes.Buffer
 		enc = expfmt.NewEncoder(&buf2, expfmt.FmtText)
-		for _, mf := range normalizeMetricFamilies(expectedMetrics) {
+		for _, mf := range internal.NormalizeMetricFamilies(expectedMetrics) {
 			if err := enc.Encode(mf); err != nil {
 				return fmt.Errorf("encoding result failed: %s", err)
 			}
@@ -100,64 +100,3 @@ func filterMetrics(metrics []*dto.MetricFamily, names []string) []*dto.MetricFam
 	}
 	return filtered
 }
-
-// The below sorting code is copied form the Prometheus client library modulo the added
-// label pair sorting.
-// https://github.com/prometheus/client_golang/blob/ea6e1db4cb8127eeb0b6954f7320363e5451820f/prometheus/registry.go#L642-L684
-
-// metricSorter is a sortable slice of *dto.Metric.
-type metricSorter []*dto.Metric
-
-func (s metricSorter) Len() int {
-	return len(s)
-}
-
-func (s metricSorter) Swap(i, j int) {
-	s[i], s[j] = s[j], s[i]
-}
-
-func (s metricSorter) Less(i, j int) bool {
-	sort.Sort(prometheus.LabelPairSorter(s[i].Label))
-	sort.Sort(prometheus.LabelPairSorter(s[j].Label))
-
-	if len(s[i].Label) != len(s[j].Label) {
-		return len(s[i].Label) < len(s[j].Label)
-	}
-
-	for n, lp := range s[i].Label {
-		vi := lp.GetValue()
-		vj := s[j].Label[n].GetValue()
-		if vi != vj {
-			return vi < vj
-		}
-	}
-
-	if s[i].TimestampMs == nil {
-		return false
-	}
-	if s[j].TimestampMs == nil {
-		return true
-	}
-	return s[i].GetTimestampMs() < s[j].GetTimestampMs()
-}
-
-// normalizeMetricFamilies returns a MetricFamily slice with empty
-// MetricFamilies pruned and the remaining MetricFamilies sorted by name within
-// the slice, with the contained Metrics sorted within each MetricFamily.
-func normalizeMetricFamilies(metricFamiliesByName map[string]*dto.MetricFamily) []*dto.MetricFamily {
-	for _, mf := range metricFamiliesByName {
-		sort.Sort(metricSorter(mf.Metric))
-	}
-	names := make([]string, 0, len(metricFamiliesByName))
-	for name, mf := range metricFamiliesByName {
-		if len(mf.Metric) > 0 {
-			names = append(names, name)
-		}
-	}
-	sort.Strings(names)
-	result := make([]*dto.MetricFamily, 0, len(names))
-	for _, name := range names {
-		result = append(result, metricFamiliesByName[name])
-	}
-	return result
-}