smart diff to testutil.GatherAndCompare

go.mod

@@ -8,6 +8,7 @@ require (
 	github.com/prometheus/client_model v0.2.0
 	github.com/prometheus/common v0.32.1
 	github.com/prometheus/procfs v0.7.3
+	github.com/stretchr/testify v1.4.0
 	golang.org/x/sys v0.0.0-20220114195835-da31bd327af9
 	google.golang.org/protobuf v1.26.0
 )

prometheus/testutil/testutil.go

@@ -41,8 +41,10 @@ import (
 	"bytes"
 	"fmt"
 	"io"
+	"testing"
 
 	"github.com/prometheus/common/expfmt"
+	"github.com/stretchr/testify/require"
 
 	dto "github.com/prometheus/client_model/go"
 
@@ -215,13 +217,79 @@ func compare(got, want []*dto.MetricFamily) error {
 	if wantBuf.String() != gotBuf.String() {
 		return fmt.Errorf(`
 metric output does not match expectation; want:
+%s
+got:
+%s`, wantBuf.String(), gotBuf.String())
+
+	}
+	return nil
+}
+
+// CollectAndCompareV2 is similar to CollectAndCompare except it takes *testing.T object
+// and shouldFail Flag to pass down to GatherAndCompareV2.
+func CollectAndCompareV2(t *testing.T, c prometheus.Collector, expected io.Reader, shouldFail bool, metricNames ...string) error {
+	reg := prometheus.NewPedanticRegistry()
+	if err := reg.Register(c); err != nil {
+		return fmt.Errorf("registering collector failed: %s", err)
+	}
+	return GatherAndCompareV2(t, reg, expected, shouldFail, metricNames...)
+}
+
+// GatherAndCompareV2 is similiar to GatherAndCompare except it takes t *testing.T and shouldFail flag
+// and calls TransactionalGatherAndCompareV2.
+func GatherAndCompareV2(t *testing.T, g prometheus.Gatherer, expected io.Reader, shouldFail bool, metricNames ...string) error {
+	return TransactionalGatherAndCompareV2(t, prometheus.ToTransactionalGatherer(g), expected, shouldFail, metricNames...)
+}
+
+// TransactionalGatherAndCompareV2 is similiar to TransactionalGatherAndCompare except
+// it takes t *testing.T and shouldFail flag and calls compareV2 for better diff.
+func TransactionalGatherAndCompareV2(t *testing.T, g prometheus.TransactionalGatherer, expected io.Reader, shouldFail bool, metricNames ...string) error {
+	got, done, err := g.Gather()
+	defer done()
+	if err != nil {
+		return fmt.Errorf("gathering metrics failed: %s", err)
+	}
+	if metricNames != nil {
+		got = filterMetrics(got, metricNames)
+	}
+	var tp expfmt.TextParser
+	wantRaw, err := tp.TextToMetricFamilies(expected)
+	if err != nil {
+		return fmt.Errorf("parsing expected metrics failed: %s", err)
+	}
+	want := internal.NormalizeMetricFamilies(wantRaw)
+
+	return compareV2(t, got, want, shouldFail)
+}
+
+// compareV2 accepts *testing.T object and uses require package to provide
+// a better diff between got and want.
+func compareV2(t *testing.T, got, want []*dto.MetricFamily, shouldFail bool) error {
+	var gotBuf, wantBuf bytes.Buffer
+	enc := expfmt.NewEncoder(&gotBuf, expfmt.FmtText)
+	for _, mf := range got {
+		if err := enc.Encode(mf); err != nil {
+			return fmt.Errorf("encoding gathered metrics failed: %s", err)
+		}
+	}
+	enc = expfmt.NewEncoder(&wantBuf, expfmt.FmtText)
+	for _, mf := range want {
+		if err := enc.Encode(mf); err != nil {
+			return fmt.Errorf("encoding expected metrics failed: %s", err)
+		}
+	}
+
+	if shouldFail && wantBuf.String() != gotBuf.String() {
+		return fmt.Errorf(`
+metric output does not match expectation; want:
 
 %s
 got:
 
 %s`, wantBuf.String(), gotBuf.String())
-
 	}
+
+	require.Equal(t, wantBuf.String(), gotBuf.String())
 	return nil
 }
 

prometheus/testutil/testutil_test.go

@@ -18,6 +18,7 @@ import (
 	"testing"
 
 	"github.com/prometheus/client_golang/prometheus"
+	"github.com/stretchr/testify/require"
 )
 
 type untypedCollector struct{}
@@ -138,7 +139,7 @@ func TestCollectAndCompare(t *testing.T) {
 		some_total{ label1 = "value1" } 1
 	`
 
-	if err := CollectAndCompare(c, strings.NewReader(metadata+expected), "some_total"); err != nil {
+	if err := CollectAndCompareV2(t, c, strings.NewReader(metadata+expected), false, "some_total"); err != nil {
 		t.Errorf("unexpected collecting result:\n%s", err)
 	}
 }
@@ -160,7 +161,7 @@ func TestCollectAndCompareNoLabel(t *testing.T) {
 		some_total 1
 	`
 
-	if err := CollectAndCompare(c, strings.NewReader(metadata+expected), "some_total"); err != nil {
+	if err := CollectAndCompareV2(t, c, strings.NewReader(metadata+expected), false, "some_total"); err != nil {
 		t.Errorf("unexpected collecting result:\n%s", err)
 	}
 }
@@ -232,7 +233,7 @@ func TestCollectAndCompareHistogram(t *testing.T) {
 		}
 
 		t.Run(input.name, func(t *testing.T) {
-			if err := CollectAndCompare(input.c, strings.NewReader(input.metadata+input.expect)); err != nil {
+			if err := CollectAndCompareV2(t, input.c, strings.NewReader(input.metadata+input.expect), false); err != nil {
 				t.Errorf("unexpected collecting result:\n%s", err)
 			}
 		})
@@ -259,7 +260,7 @@ func TestNoMetricFilter(t *testing.T) {
 		some_total{label1="value1"} 1
 	`
 
-	if err := CollectAndCompare(c, strings.NewReader(metadata+expected)); err != nil {
+	if err := CollectAndCompareV2(t, c, strings.NewReader(metadata+expected), false); err != nil {
 		t.Errorf("unexpected collecting result:\n%s", err)
 	}
 }
@@ -297,14 +298,12 @@ got:
 some_total{label1="value1"} 1
 `
 
-	err := CollectAndCompare(c, strings.NewReader(metadata+expected))
+	err := CollectAndCompareV2(t, c, strings.NewReader(metadata+expected), true)
 	if err == nil {
 		t.Error("Expected error, got no error.")
 	}
 
-	if err.Error() != expectedError {
-		t.Errorf("Expected\n%#+v\nGot:\n%#+v", expectedError, err.Error())
-	}
+	require.EqualErrorf(t, err, expectedError, "Expected\n%#+v\nGot:\n%#+v", expectedError, err.Error())
 }
 
 func TestCollectAndCount(t *testing.T) {