***countdown: add configurableSleeper abstraction

countdown/countdown.go

@@ -15,10 +15,23 @@ type Sleeper interface {
 	Sleep()
 }
 
-type DefaultSleeper struct{}
+type ConfigurableSleeper struct {
+	duration time.Duration
+	sleep    func(time.Duration)
+}
 
-func (d *DefaultSleeper) Sleep() {
+func NewConfigurableSleeper(
-	time.Sleep(1 * time.Second)
+	duration time.Duration,
+	sleep func(time.Duration),
+) *ConfigurableSleeper {
+	return &ConfigurableSleeper{
+		duration: duration,
+		sleep:    sleep,
+	}
+}
+
+func (s *ConfigurableSleeper) Sleep() {
+	s.sleep(s.duration)
 }
 
 func Countdown(out io.Writer, sleeper Sleeper) {

countdown/countdown_test.go

@@ -4,6 +4,7 @@ import (
 	"bytes"
 	"reflect"
 	"testing"
+	"time"
 )
 
 const (
@@ -24,6 +25,14 @@ func (s *SpyCountdownOperations) Write(p []byte) (n int, err error) {
 	return 0, nil
 }
 
+type SpyTime struct {
+	durationSlept time.Duration
+}
+
+func (s *SpyTime) Sleep(duration time.Duration) {
+	s.durationSlept = duration
+}
+
 func TestCountdown(t *testing.T) {
 	t.Run("print 3 to Go!", func(t *testing.T) {
 		buffer := &bytes.Buffer{}
@@ -54,3 +63,15 @@ Go!`
 		}
 	})
 }
+
+func TestConfigurableSleeper(t *testing.T) {
+	sleepTime := 5 * time.Second
+
+	spyTime := &SpyTime{}
+	sleeper := NewConfigurableSleeper(sleepTime, spyTime.Sleep)
+	sleeper.Sleep()
+
+	if spyTime.durationSlept != sleepTime {
+		t.Errorf("should have slept for %v but slept for %v", sleepTime, spyTime.durationSlept)
+	}
+}

main.go

@@ -3,10 +3,12 @@ package main
 import (
 	"gobytest/countdown"
 	"os"
+	"time"
 )
 
 func main() {
 	// greet.Greet(os.Stdout, "Elodie")
+	sleeper := countdown.NewConfigurableSleeper(1*time.Second, time.Sleep)
 
-	countdown.Countdown(os.Stdout, &countdown.DefaultSleeper{})
+	countdown.Countdown(os.Stdout, sleeper)
 }