expand tests for classic and exponential native histograms

Signed-off-by: Jeanette Tan <jeanette.tan@grafana.com>

scrape/scrape_test.go

@@ -3426,23 +3426,10 @@ metric: <
 >
 `, name, value)
 	}
-	genTestHistProto := func(name string) string {
+	genTestHistProto := func(name string, hasClassic, hasExponential bool) string {
-		return fmt.Sprintf(`
+		var classic string
-name: "%s"
+		if hasClassic {
-help: "This is a histogram with default buckets"
+			classic = `
-type: HISTOGRAM
-metric: <
-	label: <
-		name: "address"
-		value: "0.0.0.0"
-	>
-	label: <
-		name: "port"
-		value: "5001"
-	>
-	histogram: <
-		sample_count: 1
-		sample_sum: 10
 bucket: <
 	cumulative_count: 0
 	upper_bound: 0.005
@@ -3486,16 +3473,48 @@ metric: <
 bucket: <
 	cumulative_count: 1
 	upper_bound: 10
+>`
+		}
+		var expo string
+		if hasExponential {
+			expo = `
+schema: 3
+zero_threshold: 2.938735877055719e-39
+zero_count: 0
+positive_span: <
+	offset: 2
+	length: 1
 >
+positive_delta: 1`
+		}
+		return fmt.Sprintf(`
+name: "%s"
+help: "This is a histogram with default buckets"
+type: HISTOGRAM
+metric: <
+	label: <
+		name: "address"
+		value: "0.0.0.0"
+	>
+	label: <
+		name: "port"
+		value: "5001"
+	>
+	histogram: <
+		sample_count: 1
+		sample_sum: 10
+		%s
+		%s
 	>
 	timestamp_ms: 1234568
 >
-`, name)
+`, name, classic, expo)
 	}
 
 	metricsTexts := map[string]struct {
 		text           []string
 		contentType    string
+		hasExponential bool
 	}{
 		"text": {
 			text: []string{
@@ -3520,25 +3539,37 @@ metric: <
 		"protobuf": {
 			text: []string{
 				genTestCounterProto("test_metric_1", 1),
-				genTestHistProto("test_histogram_1"),
+				genTestHistProto("test_histogram_1", true, false),
 				genTestCounterProto("test_metric_2", 1),
-				genTestHistProto("test_histogram_2"),
+				genTestHistProto("test_histogram_2", true, false),
 				genTestCounterProto("test_metric_3", 1),
-				genTestHistProto("test_histogram_3"),
+				genTestHistProto("test_histogram_3", true, false),
 			},
 			contentType: "application/vnd.google.protobuf",
 		},
 		"protobuf, in different order": {
 			text: []string{
-				genTestHistProto("test_histogram_1"),
+				genTestHistProto("test_histogram_1", true, false),
 				genTestCounterProto("test_metric_1", 1),
-				genTestHistProto("test_histogram_2"),
+				genTestHistProto("test_histogram_2", true, false),
 				genTestCounterProto("test_metric_2", 1),
-				genTestHistProto("test_histogram_3"),
+				genTestHistProto("test_histogram_3", true, false),
 				genTestCounterProto("test_metric_3", 1),
 			},
 			contentType: "application/vnd.google.protobuf",
 		},
+		"protobuf, with native exponential histogram": {
+			text: []string{
+				genTestCounterProto("test_metric_1", 1),
+				genTestHistProto("test_histogram_1", true, true),
+				genTestCounterProto("test_metric_2", 1),
+				genTestHistProto("test_histogram_2", true, true),
+				genTestCounterProto("test_metric_3", 1),
+				genTestHistProto("test_histogram_3", true, true),
+			},
+			contentType:    "application/vnd.google.protobuf",
+			hasExponential: true,
+		},
 	}
 
 	checkBucketValues := func(expectedCount int, contentType string, series storage.SeriesSet) {
@@ -3746,8 +3777,12 @@ metric: <
 					checkBucketValues(tc.expectedClassicHistCount, metricsText.contentType, series)
 
 					series = q.Select(ctx, false, nil, labels.MustNewMatcher(labels.MatchRegexp, "__name__", fmt.Sprintf("test_histogram_%d", i)))
+					if metricsText.hasExponential {
+						checkHistSeries(series, 1, 3)
+					} else {
 						checkHistSeries(series, tc.expectedNhcbCount, histogram.CustomBucketsSchema)
 					}
+				}
 			})
 		}
 	}