1 files changed, 136 insertions, 0 deletions
diff --git a/src/go/collectors/go.d.plugin/pkg/metrics/histogram_test.go b/src/go/collectors/go.d.plugin/pkg/metrics/histogram_test.go
new file mode 100644
index 000000000..91266915c
--- /dev/null
+++ b/src/go/collectors/go.d.plugin/pkg/metrics/histogram_test.go
@@ -0,0 +1,136 @@
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+package metrics
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestLinearBuckets(t *testing.T) {
+	buckets := LinearBuckets(0, 1, 10)
+	assert.Len(t, buckets, 10)
+	assert.EqualValues(t, 0, buckets[0])
+	assert.EqualValues(t, 5.0, buckets[5])
+	assert.EqualValues(t, 9.0, buckets[9])
+
+	assert.Panics(t, func() {
+		LinearBuckets(0, 1, 0)
+	})
+}
+
+func TestExponentialBuckets(t *testing.T) {
+	buckets := ExponentialBuckets(1, 2, 10)
+	assert.Len(t, buckets, 10)
+	assert.EqualValues(t, 1, buckets[0])
+	assert.EqualValues(t, 32.0, buckets[5])
+	assert.EqualValues(t, 512.0, buckets[9])
+
+	assert.Panics(t, func() {
+		ExponentialBuckets(1, 2, 0)
+	})
+	assert.Panics(t, func() {
+		ExponentialBuckets(0, 2, 2)
+	})
+
+	assert.Panics(t, func() {
+		ExponentialBuckets(1, 1, 2)
+	})
+}
+
+func TestNewHistogram(t *testing.T) {
+	h := NewHistogram(nil).(*histogram)
+	assert.EqualValues(t, 0, h.count)
+	assert.EqualValues(t, 0.0, h.sum)
+	assert.Equal(t, DefBuckets, h.upperBounds)
+
+	h = NewHistogram([]float64{1, 10, 5}).(*histogram)
+	assert.Equal(t, []float64{1, 5, 10}, h.upperBounds)
+	assert.Len(t, h.buckets, 3)
+}
+
+func TestHistogram_WriteTo(t *testing.T) {
+	h := NewHistogram([]float64{1, 2, 3})
+	m := map[string]int64{}
+	h.WriteTo(m, "pi", 100, 1)
+	assert.Len(t, m, 5)
+	assert.EqualValues(t, 0, m["pi_count"])
+	assert.EqualValues(t, 0, m["pi_sum"])
+	assert.EqualValues(t, 0, m["pi_bucket_1"])
+	assert.EqualValues(t, 0, m["pi_bucket_2"])
+	assert.EqualValues(t, 0, m["pi_bucket_3"])
+
+	h.Observe(0)
+	h.Observe(1.5)
+	h.Observe(3.5)
+	h.WriteTo(m, "pi", 100, 1)
+	assert.Len(t, m, 5)
+	assert.EqualValues(t, 3, m["pi_count"])
+	assert.EqualValues(t, 500, m["pi_sum"])
+	assert.EqualValues(t, 1, m["pi_bucket_1"])
+	assert.EqualValues(t, 2, m["pi_bucket_2"])
+	assert.EqualValues(t, 2, m["pi_bucket_3"])
+}
+
+func TestHistogram_searchBucketIndex(t *testing.T) {
+	h := NewHistogram(LinearBuckets(1, 1, 5)).(*histogram) // [1, 2, ..., 5]
+	assert.Equal(t, 0, h.searchBucketIndex(0.1))
+	assert.Equal(t, 1, h.searchBucketIndex(1.1))
+	assert.Equal(t, 5, h.searchBucketIndex(8.1))
+
+	h = NewHistogram(LinearBuckets(1, 1, 40)).(*histogram) // [1, 2, ..., 5]
+	assert.Equal(t, 0, h.searchBucketIndex(0.1))
+	assert.Equal(t, 1, h.searchBucketIndex(1.1))
+	assert.Equal(t, 5, h.searchBucketIndex(5.1))
+	assert.Equal(t, 7, h.searchBucketIndex(8))
+	assert.Equal(t, 39, h.searchBucketIndex(39.5))
+	assert.Equal(t, 40, h.searchBucketIndex(40.5))
+}
+
+func BenchmarkHistogram_Observe(b *testing.B) {
+	benchmarks := []struct {
+		name    string
+		buckets []float64
+	}{
+		{"default", nil},
+		{"len_10", LinearBuckets(0, 0.1, 10)},
+		{"len_20", LinearBuckets(0, 0.1, 20)},
+		{"len_30", LinearBuckets(0, 0.1, 30)},
+		{"len_40", LinearBuckets(0, 0.1, 40)},
+	}
+	for _, bm := range benchmarks {
+		b.Run(bm.name, func(b *testing.B) {
+			h := NewHistogram(bm.buckets)
+			for i := 0; i < b.N; i++ {
+				h.Observe(2.5)
+			}
+		})
+	}
+}
+
+func BenchmarkHistogram_WriteTo(b *testing.B) {
+	benchmarks := []struct {
+		name    string
+		buckets []float64
+	}{
+		{"default", nil},
+		{"len_10", LinearBuckets(0, 0.1, 10)},
+		{"len_20", LinearBuckets(0, 0.1, 20)},
+		{"len_30", LinearBuckets(0, 0.1, 30)},
+		{"len_40", LinearBuckets(0, 0.1, 40)},
+	}
+	for _, bm := range benchmarks {
+		b.Run(bm.name, func(b *testing.B) {
+			h := NewHistogram(bm.buckets)
+			h.Observe(0.1)
+			h.Observe(0.01)
+			h.Observe(0.5)
+			h.Observe(10)
+			m := map[string]int64{}
+			for i := 0; i < b.N; i++ {
+				h.WriteTo(m, "pi", 100, 1)
+			}
+		})
+	}
+}