random accepts generator

src/device/input/input.go

@@ -5,5 +5,5 @@ type Input interface {
 }
 
 func New() Input {
-	return NewRandom('a', 'g')
+	return NewRandom(RandomCharFromRange('a', 'g'))
 }

src/device/input/random.go

@@ -11,14 +11,13 @@ type Button struct {
 }
 
 type Random struct {
-	start byte
-	stop  byte
-	down  []Button
+	generator func() byte
+	down      []Button
 }
 
-func NewRandom(start, stop byte) *Random {
+func NewRandom(generator func() byte) *Random {
 	rand.Seed(time.Now().UnixNano())
-	return &Random{start: start, stop: stop}
+	return &Random{generator: generator}
 }
 
 func (r *Random) Read() []Button {
@@ -30,8 +29,14 @@ func (r *Random) Read() []Button {
 		r.down = r.down[:0]
 		return was
 	} else {
-		c := Button{Char: r.start + byte(rand.Int()%int(1+r.stop-r.start)), Down: true}
+		c := Button{Char: r.generator(), Down: true}
 		r.down = append(r.down, c)
 		return []Button{c}
 	}
 }
+
+func RandomCharFromRange(start, stop byte) func() byte {
+	return func() byte {
+		return start + byte(rand.Int()%int(1+stop-start))
+	}
+}

src/device/input/random_test.go

@@ -6,7 +6,7 @@ import (
 )
 
 func TestRandom(t *testing.T) {
-	r := input.NewRandom('a', 'g')
+	r := input.NewRandom(input.RandomCharFromRange('a', 'z'))
 	for i := 0; i < 100; i++ {
 		batch := r.Read()
 		for _, got := range batch {