chore: add the timeSource interface

cache.go

@@ -63,6 +63,12 @@ type expiryPolicy[K comparable, V any] interface {
 	Clear()
 }
 
+type timeSource interface {
+	Init()
+	Offset() int64
+	Time(offset int64) time.Time
+}
+
 // Cache is a structure performs a best-effort bounding of a hash table using eviction algorithm
 // to determine which entries to evict when the capacity is exceeded.
 type Cache[K comparable, V any] struct {
@@ -72,7 +78,7 @@ type Cache[K comparable, V any] struct {
 	expiryPolicy   expiryPolicy[K, V]
 	stats          statsRecorder
 	logger         Logger
-	clock          *clock.Clock
+	clock          timeSource
 	stripedBuffer  *lossy.Striped[K, V]
 	writeBuffer    *queue.Growable[task[K, V]]
 	singleflight   *group[K, V]
@@ -123,7 +129,7 @@ func newCache[K comparable, V any](b *Builder[K, V]) *Cache[K, V] {
 		doneClose:     make(chan struct{}, 1),
 		weigher:       b.getWeigher(),
 		onDeletion:    b.onDeletion,
-		clock:         &clock.Clock{},
+		clock:         &clock.Real{},
 	}
 
 	if _, ok := b.statsRecorder.(noopStatsRecorder); ok {

internal/clock/clock.go → internal/clock/real.go

@@ -20,13 +20,13 @@ import (
 	"time"
 )
 
-type Clock struct {
+type Real struct {
 	start         time.Time
 	initMutex     sync.Mutex
 	isInitialized atomic.Bool
 }
 
-func (c *Clock) Init() {
+func (c *Real) Init() {
 	if !c.isInitialized.Load() {
 		c.initMutex.Lock()
 		if !c.isInitialized.Load() {
@@ -37,13 +37,13 @@ func (c *Clock) Init() {
 	}
 }
 
-func (c *Clock) Offset() int64 {
+func (c *Real) Offset() int64 {
 	if !c.isInitialized.Load() {
 		return 0
 	}
 	return time.Since(c.start).Nanoseconds()
 }
 
-func (c *Clock) Time(offset int64) time.Time {
+func (c *Real) Time(offset int64) time.Time {
 	return c.start.Add(time.Duration(offset))
 }

internal/clock/clock_bench_test.go → internal/clock/real_bench_test.go

@@ -46,11 +46,12 @@ func BenchmarkNanotime(b *testing.B) {
 	})
 }
 
-func BenchmarkClock(b *testing.B) {
+func BenchmarkReal(b *testing.B) {
 	b.ReportAllocs()
 	b.RunParallel(func(pb *testing.PB) {
 		var ts int64
-		c := New()
+		c := &Real{}
+		c.Init()
 		for pb.Next() {
 			ts += c.Offset()
 		}

internal/clock/clock_test.go → internal/clock/real_test.go

@@ -20,7 +20,8 @@ import (
 )
 
 func TestNow(t *testing.T) {
-	c := New()
+	c := &Real{}
+	c.Init()
 
 	got := c.Offset() / 1e9
 	if got != 0 {