utils: add DeepEqual replacement using go-cmp

go-cmp allows control over how unexported fields and implementation
details are handled.

Signed-off-by: Bryan Boreham <bjboreham@gmail.com>

go.mod

@@ -28,6 +28,7 @@ require (
 	github.com/go-zookeeper/zk v1.0.3
 	github.com/gogo/protobuf v1.3.2
 	github.com/golang/snappy v0.0.4
+	github.com/google/go-cmp v0.6.0
 	github.com/google/pprof v0.0.0-20240117000934-35fc243c5815
 	github.com/google/uuid v1.5.0
 	github.com/gophercloud/gophercloud v1.8.0
@@ -135,7 +136,6 @@ require (
 	github.com/golang/groupcache v0.0.0-20210331224755-41bb18bfe9da // indirect
 	github.com/golang/protobuf v1.5.3 // indirect
 	github.com/google/gnostic-models v0.6.8 // indirect
-	github.com/google/go-cmp v0.6.0 // indirect
 	github.com/google/go-querystring v1.1.0 // indirect
 	github.com/google/gofuzz v1.2.0 // indirect
 	github.com/google/s2a-go v0.1.7 // indirect

util/testutil/cmp.go

@@ -0,0 +1,43 @@
+// Copyright 2023 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
+
+import (
+	"fmt"
+	"testing"
+
+	"github.com/google/go-cmp/cmp"
+	"github.com/stretchr/testify/require"
+
+	"github.com/prometheus/prometheus/model/labels"
+)
+
+// Replacement for require.Equal using go-cmp adapted for Prometheus data structures, instead of DeepEqual.
+func RequireEqual(t testing.TB, expected, actual interface{}, msgAndArgs ...interface{}) {
+	t.Helper()
+	RequireEqualWithOptions(t, expected, actual, nil, msgAndArgs...)
+}
+
+// As RequireEqual but allows extra cmp.Options.
+func RequireEqualWithOptions(t testing.TB, expected, actual interface{}, extra []cmp.Option, msgAndArgs ...interface{}) {
+	t.Helper()
+	options := append([]cmp.Option{cmp.Comparer(labels.Equal)}, extra...)
+	if cmp.Equal(expected, actual, options...) {
+		return
+	}
+	diff := cmp.Diff(expected, actual, options...)
+	require.Fail(t, fmt.Sprintf("Not equal: \n"+
+		"expected: %s\n"+
+		"actual  : %s%s", expected, actual, diff), msgAndArgs...)
+}