Add tests for pkg/util/test.AssertGatherAndCompare

pkg/util/test/metrics.go

@@ -11,7 +11,7 @@ import (
 
 	"github.com/prometheus/client_golang/prometheus"
 	"github.com/prometheus/client_golang/prometheus/testutil"
-	"github.com/stretchr/testify/require"
+	"github.com/stretchr/testify/assert"
 )
 
 type ExpectedMetricsContext struct {
@@ -67,7 +67,20 @@ func (m *ExpectedMetrics) GetNames() []string {
 	return m.Names
 }
 
+// AssertGatherAndCompare asserts that metrics in expectedText are found among g's metrics.
+// If, however, any metrics are provided, the following rules apply:
+// * Provided metrics that also exist in expectedText are required to be found among g's metrics.
+// * Provided metrics that don't exist in expectedText are required to be absent from g's metrics.
 func AssertGatherAndCompare(t *testing.T, g prometheus.Gatherer, expectedText string, metrics ...string) {
+	t.Helper()
+	assert.NoError(t, gatherAndCompare(g, expectedText, metrics...))
+}
+
+func gatherAndCompare(g prometheus.Gatherer, expectedText string, metrics ...string) error {
+	if len(metrics) == 0 {
+		return testutil.GatherAndCompare(g, strings.NewReader(expectedText))
+	}
+
 	sc := bufio.NewScanner(strings.NewReader(expectedText))
 	absent := make([]string, len(metrics))
 	copy(absent, metrics)
@@ -85,17 +98,31 @@ func AssertGatherAndCompare(t *testing.T, g prometheus.Gatherer, expectedText st
 			}
 		}
 	}
-	require.Equal(t, len(metrics), len(required)+len(absent)) // Sanity check.
+	// Sanity check.
+	if len(required)+len(absent) != len(metrics) {
+		panic(fmt.Errorf("length of required+absent doesn't match up with metrics"))
+	}
+
 	if len(required) > 0 {
-		require.NoError(t, testutil.GatherAndCompare(g, strings.NewReader(expectedText), required...), "should be present: metrics=%s", strings.Join(required, ", "))
+		if err := testutil.GatherAndCompare(g, strings.NewReader(expectedText), required...); err != nil {
+			return err
+		}
 	}
+
 	notAbsent := []string{}
 	for _, metric := range absent {
 		count, err := testutil.GatherAndCount(g, metric)
-		require.NoError(t, err)
+		if err != nil {
+			return fmt.Errorf("GatherAndCount(g, %s): %w", metric, err)
+		}
+
 		if count > 0 {
 			notAbsent = append(notAbsent, metric)
 		}
 	}
-	require.Empty(t, notAbsent, "should be absent: metrics=%s", strings.Join(notAbsent, ", "))
+	if len(notAbsent) > 0 {
+		return fmt.Errorf("should be absent: metrics=%s", strings.Join(notAbsent, ", "))
+	}
+
+	return nil
 }

pkg/util/test/metrics_test.go

@@ -0,0 +1,126 @@
+// SPDX-License-Identifier: AGPL-3.0-only
+
+package test
+
+import (
+	"testing"
+
+	dto "github.com/prometheus/client_model/go"
+	"github.com/stretchr/testify/require"
+	"google.golang.org/protobuf/proto"
+)
+
+func TestAssertGatherAndCompare(t *testing.T) {
+	g := fakeGatherer{
+		metrics: []*dto.MetricFamily{
+			{
+				Name: proto.String("cortex_distributor_deduped_samples_total"),
+				Help: proto.String("The total number of deduplicated samples."),
+				Metric: []*dto.Metric{
+					{
+						Label: []*dto.LabelPair{
+							{
+								Name:  proto.String("environment"),
+								Value: proto.String("test"),
+							},
+						},
+						TimestampMs: proto.Int64(1000),
+						Counter: &dto.Counter{
+							Value: proto.Float64(1),
+						},
+					},
+				},
+			},
+		},
+	}
+
+	t.Run("don't specify any metrics", func(t *testing.T) {
+		// When not specifying any metrics, an error should be returned due to missing metric
+		// cortex_distributor_latest_seen_sample_timestamp_seconds.
+		err := gatherAndCompare(g, `
+		# HELP cortex_distributor_deduped_samples_total The total number of deduplicated samples.
+		# TYPE cortex_distributor_deduped_samples_total counter
+		cortex_distributor_deduped_samples_total{environment="test"} 1 1000
+
+		# HELP cortex_distributor_latest_seen_sample_timestamp_seconds Unix timestamp of latest received sample per user.
+		# TYPE cortex_distributor_latest_seen_sample_timestamp_seconds gauge
+		cortex_distributor_latest_seen_sample_timestamp_seconds{user="userA"} 1111
+		`)
+		require.EqualError(t, err, ` # HELP cortex_distributor_deduped_samples_total The total number of deduplicated samples.
+ # TYPE cortex_distributor_deduped_samples_total counter
+ cortex_distributor_deduped_samples_total{environment="test"} 1 1000
++# HELP cortex_distributor_latest_seen_sample_timestamp_seconds Unix timestamp of latest received sample per user.
++# TYPE cortex_distributor_latest_seen_sample_timestamp_seconds gauge
++cortex_distributor_latest_seen_sample_timestamp_seconds{user="userA"} 1111
+ `)
+	})
+
+	t.Run("specify required metric", func(t *testing.T) {
+		// When specifying that cortex_distributor_deduped_samples_total as the one required metric,
+		// cortex_distributor_latest_seen_sample_timestamp_seconds should be ignored even if it's missing.
+		AssertGatherAndCompare(t, g, `
+		# HELP cortex_distributor_deduped_samples_total The total number of deduplicated samples.
+		# TYPE cortex_distributor_deduped_samples_total counter
+		cortex_distributor_deduped_samples_total{environment="test"} 1 1000
+
+		# HELP cortex_distributor_latest_seen_sample_timestamp_seconds Unix timestamp of latest received sample per user.
+		# TYPE cortex_distributor_latest_seen_sample_timestamp_seconds gauge
+		cortex_distributor_latest_seen_sample_timestamp_seconds{user="userA"} 1111
+		`, "cortex_distributor_deduped_samples_total")
+	})
+
+	t.Run("specify required metric which isn't there", func(t *testing.T) {
+		// When specifying that cortex_distributor_deduped_samples_total as the one required metric,
+		// cortex_distributor_latest_seen_sample_timestamp_seconds should be ignored even if it's missing.
+		err := gatherAndCompare(g, `
+		# HELP cortex_distributor_deduped_samples_total The total number of deduplicated samples.
+		# TYPE cortex_distributor_deduped_samples_total counter
+		cortex_distributor_deduped_samples_total{environment="test"} 1 1000
+
+		# HELP cortex_distributor_latest_seen_sample_timestamp_seconds Unix timestamp of latest received sample per user.
+		# TYPE cortex_distributor_latest_seen_sample_timestamp_seconds gauge
+		cortex_distributor_latest_seen_sample_timestamp_seconds{user="userA"} 1111
+		`, "cortex_distributor_latest_seen_sample_timestamp_seconds")
+		require.EqualError(t, err, "expected metric name(s) not found: [cortex_distributor_latest_seen_sample_timestamp_seconds]")
+	})
+
+	t.Run("specify required metric and absent metric", func(t *testing.T) {
+		// Verify that cortex_distributor_deduped_samples_total is found among metrics returned by g,
+		// and that conversely, cortex_distributor_non_ha_samples_received_total is not found among
+		// metrics returned by g.
+		// cortex_distributor_latest_seen_sample_timestamp_seconds is ignored, since it's not among
+		// the specified metrics.
+		AssertGatherAndCompare(t, g, `
+		# HELP cortex_distributor_deduped_samples_total The total number of deduplicated samples.
+		# TYPE cortex_distributor_deduped_samples_total counter
+		cortex_distributor_deduped_samples_total{environment="test"} 1 1000
+
+		# HELP cortex_distributor_latest_seen_sample_timestamp_seconds Unix timestamp of latest received sample per user.
+		# TYPE cortex_distributor_latest_seen_sample_timestamp_seconds gauge
+		cortex_distributor_latest_seen_sample_timestamp_seconds{user="userA"} 1111
+		`, "cortex_distributor_deduped_samples_total", "cortex_distributor_non_ha_samples_received_total")
+	})
+
+	t.Run("specify absent metric which is actually there", func(t *testing.T) {
+		// Verify that cortex_distributor_deduped_samples_total is found among metrics returned by g,
+		// and that conversely, cortex_distributor_non_ha_samples_received_total is not found among
+		// metrics returned by g.
+		// cortex_distributor_latest_seen_sample_timestamp_seconds is ignored, since it's not among
+		// the specified metrics.
+		err := gatherAndCompare(g, `
+		# HELP cortex_distributor_latest_seen_sample_timestamp_seconds Unix timestamp of latest received sample per user.
+		# TYPE cortex_distributor_latest_seen_sample_timestamp_seconds gauge
+		cortex_distributor_latest_seen_sample_timestamp_seconds{user="userA"} 1111
+		`, "cortex_distributor_deduped_samples_total", "cortex_distributor_non_ha_samples_received_total")
+		require.EqualError(t, err, "should be absent: metrics=cortex_distributor_deduped_samples_total")
+	})
+}
+
+type fakeGatherer struct {
+	metrics []*dto.MetricFamily
+	err     error
+}
+
+func (g fakeGatherer) Gather() ([]*dto.MetricFamily, error) {
+	return g.metrics, g.err
+}