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package statsengine
import (
"reflect"
"testing"
)
func TestHistogramBucketIndexBoundaries(t *testing.T) {
tests := []struct {
name string
dur uint64
idx int
}{
{name: "zero", dur: 0, idx: 0},
{name: "just below 1us", dur: 999, idx: 0},
{name: "at 1us", dur: 1_000, idx: 1},
{name: "at 10us", dur: 10_000, idx: 2},
{name: "at 100us", dur: 100_000, idx: 3},
{name: "at 1ms", dur: 1_000_000, idx: 4},
{name: "at 10ms", dur: 10_000_000, idx: 5},
{name: "at 100ms", dur: 100_000_000, idx: 6},
{name: "at 1s", dur: 1_000_000_000, idx: 7},
{name: "above 1s", dur: 5_000_000_000, idx: 7},
}
for _, tc := range tests {
t.Run(tc.name, func(t *testing.T) {
if got := histogramBucketIndex(tc.dur); got != tc.idx {
t.Fatalf("wrong bucket index for %d: got %d want %d", tc.dur, got, tc.idx)
}
})
}
}
func TestHistogramSnapshotCountsAndRanges(t *testing.T) {
h := newHistogram()
h.Increment(0)
h.Increment(1_000)
h.Increment(1_000)
h.Increment(1_500_000_000)
snap := h.Snapshot()
if snap.Total != 4 {
t.Fatalf("wrong total: got %d want 4", snap.Total)
}
buckets := snap.Buckets()
if len(buckets) != histogramBucketCount {
t.Fatalf("wrong bucket count: got %d want %d", len(buckets), histogramBucketCount)
}
if buckets[0].Count != 1 || buckets[1].Count != 2 || buckets[7].Count != 1 {
t.Fatalf("unexpected bucket counts: %+v", buckets)
}
if buckets[0].LowerNs != 0 || buckets[0].UpperNs != 1_000 {
t.Fatalf("unexpected first range: %+v", buckets[0])
}
if buckets[7].LowerNs != 1_000_000_000 || buckets[7].UpperNs != 0 {
t.Fatalf("unexpected last range: %+v", buckets[7])
}
}
func TestHistogramSnapshotIsDefensive(t *testing.T) {
h := newHistogram()
h.Increment(1)
s1 := h.Snapshot()
b1 := s1.Buckets()
b1[0].Count = 99
s2 := h.Snapshot()
if got := s2.Buckets()[0].Count; got != 1 {
t.Fatalf("snapshot leaked mutable buckets: got %d", got)
}
if reflect.DeepEqual(b1, s2.Buckets()) {
t.Fatalf("expected defensive copies of buckets")
}
}
func TestNilHistogramSnapshot(t *testing.T) {
var h *histogram
s := h.Snapshot()
if s.Total != 0 {
t.Fatalf("expected zero total, got %d", s.Total)
}
if got := s.Buckets(); got != nil {
t.Fatalf("expected nil buckets, got %#v", got)
}
}
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