[***]countdown: mock with sequence

countdown/countdown_test.go

@@ -2,22 +2,32 @@ package countdown
 
 import (
 	"bytes"
+	"reflect"
 	"testing"
 )
 
-type SpySleeper struct {
-	Calls int
+const (
+	write = "write"
+	sleep = "sleep"
+)
+
+type SpyCountdownOperations struct {
+	Calls []string
 }
 
-func (s *SpySleeper) Sleep() {
-	s.Calls++
+func (s *SpyCountdownOperations) Sleep() {
+	s.Calls = append(s.Calls, sleep)
+}
+
+func (s *SpyCountdownOperations) Write(p []byte) (n int, err error) {
+	s.Calls = append(s.Calls, write)
+	return 0, nil
 }
 
 func TestCountdown(t *testing.T) {
+	t.Run("print 3 to Go!", func(t *testing.T) {
 		buffer := &bytes.Buffer{}
-	sleeper := &SpySleeper{}
-
-	Countdown(buffer, sleeper)
+		Countdown(buffer, &SpyCountdownOperations{})
 
 		got := buffer.String()
 		want := `3
@@ -28,8 +38,19 @@ Go!`
 		if got != want {
 			t.Errorf("got %q want %q", got, want)
 		}
+	})
 
-	if sleeper.Calls != 3 {
-		t.Errorf("not enough calls to sleeper, want 3 got %d", sleeper.Calls)
+	t.Run("sleep before every print", func(t *testing.T) {
+		spySleepPrinter := &SpyCountdownOperations{}
+
+		Countdown(spySleepPrinter, spySleepPrinter)
+
+		want := []string{
+			write, sleep, write, sleep, write, sleep, write,
 		}
+
+		if !reflect.DeepEqual(want, spySleepPrinter.Calls) {
+			t.Errorf("wanted %v got %v", want, spySleepPrinter.Calls)
+		}
+	})
 }