scrape tests: check NaN values directly

Normally, a NaN value is never equal to any other value. Compare sample
values via `Float64bits` so that NaN values which are exactly the same
will compare equal.

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

scrape/helpers_test.go

@@ -18,6 +18,7 @@ import (
 	"context"
 	"encoding/binary"
 	"fmt"
+	"math"
 	"math/rand"
 	"strings"
 	"sync"
@@ -71,6 +72,11 @@ type floatSample struct {
 	f      float64
 }
 
+func equalFloatSamples(a, b floatSample) bool {
+	// Compare Float64bits so NaN values which are exactly the same will compare equal.
+	return labels.Equal(a.metric, b.metric) && a.t == b.t && math.Float64bits(a.f) == math.Float64bits(b.f)
+}
+
 type histogramSample struct {
 	t  int64
 	h  *histogram.Histogram

scrape/scrape_test.go

@@ -1342,7 +1342,7 @@ func TestScrapeLoopAppend(t *testing.T) {
 			scrapeLabels:    `metric NaN`,
 			discoveryLabels: nil,
 			expLset:         labels.FromStrings("__name__", "metric"),
-			expValue:        float64(value.NormalNaN),
+			expValue:        math.Float64frombits(value.NormalNaN),
 		},
 	}
 
@@ -1376,13 +1376,6 @@ func TestScrapeLoopAppend(t *testing.T) {
 			},
 		}
 
-		// When the expected value is NaN
-		// DeepEqual will report NaNs as being different,
-		// so replace it with the expected one.
-		if test.expValue == float64(value.NormalNaN) {
-			app.resultFloats[0].f = expected[0].f
-		}
-
 		t.Logf("Test:%s", test.title)
 		requireEqual(t, expected, app.resultFloats)
 	}
@@ -1390,7 +1383,7 @@ func TestScrapeLoopAppend(t *testing.T) {
 
 func requireEqual(t *testing.T, expected, actual interface{}, msgAndArgs ...interface{}) {
 	testutil.RequireEqualWithOptions(t, expected, actual,
-		[]cmp.Option{cmp.AllowUnexported(floatSample{}), cmp.AllowUnexported(histogramSample{})},
+		[]cmp.Option{cmp.Comparer(equalFloatSamples), cmp.AllowUnexported(histogramSample{})},
 		msgAndArgs...)
 }
 
@@ -1691,7 +1684,6 @@ func TestScrapeLoop_ChangingMetricString(t *testing.T) {
 	require.NoError(t, err)
 	require.NoError(t, slApp.Commit())
 
-	// DeepEqual will report NaNs as being different, so replace with a different value.
 	want := []floatSample{
 		{
 			metric: labels.FromStrings("__name__", "metric_a", "a", "1", "b", "1"),
@@ -1723,11 +1715,6 @@ func TestScrapeLoopAppendStaleness(t *testing.T) {
 	require.NoError(t, err)
 	require.NoError(t, slApp.Commit())
 
-	ingestedNaN := math.Float64bits(app.resultFloats[1].f)
-	require.Equal(t, value.StaleNaN, ingestedNaN, "Appended stale sample wasn't as expected")
-
-	// DeepEqual will report NaNs as being different, so replace with a different value.
-	app.resultFloats[1].f = 42
 	want := []floatSample{
 		{
 			metric: labels.FromStrings(model.MetricNameLabel, "metric_a"),
@@ -1737,10 +1724,10 @@ func TestScrapeLoopAppendStaleness(t *testing.T) {
 		{
 			metric: labels.FromStrings(model.MetricNameLabel, "metric_a"),
 			t:      timestamp.FromTime(now.Add(time.Second)),
-			f:      42,
+			f:      math.Float64frombits(value.StaleNaN),
 		},
 	}
-	require.Equal(t, want, app.resultFloats, "Appended samples not as expected:\n%s", appender)
+	requireEqual(t, want, app.resultFloats, "Appended samples not as expected:\n%s", appender)
 }
 
 func TestScrapeLoopAppendNoStalenessIfTimestamp(t *testing.T) {
@@ -1783,8 +1770,6 @@ func TestScrapeLoopAppendStalenessIfTrackTimestampStaleness(t *testing.T) {
 	require.NoError(t, err)
 	require.NoError(t, slApp.Commit())
 
-	// DeepEqual will report NaNs as being different, so replace with a different value.
-	app.resultFloats[1].f = 42
 	want := []floatSample{
 		{
 			metric: labels.FromStrings(model.MetricNameLabel, "metric_a"),
@@ -1794,10 +1779,10 @@ func TestScrapeLoopAppendStalenessIfTrackTimestampStaleness(t *testing.T) {
 		{
 			metric: labels.FromStrings(model.MetricNameLabel, "metric_a"),
 			t:      timestamp.FromTime(now.Add(time.Second)),
-			f:      42,
+			f:      math.Float64frombits(value.StaleNaN),
 		},
 	}
-	require.Equal(t, want, app.resultFloats, "Appended samples not as expected:\n%s", appender)
+	requireEqual(t, want, app.resultFloats, "Appended samples not as expected:\n%s", appender)
 }
 
 func TestScrapeLoopAppendExemplar(t *testing.T) {