Uses NewTimer() instead of time.After() to be more

efficient since the later creates new timers in a
tight loop.

- Adds more assertions to tests
- Adds some comments to help contributors understand
that the send occurs after the Once.

Signed-off-by: Warren Fernandes <warren.f.fernandes@gmail.com>

drivers/gpio/analog_sensor_driver.go

@@ -58,6 +58,8 @@ func NewAnalogSensorDriver(a AnalogReader, pin string, v ...time.Duration) *Anal
 func (a *AnalogSensorDriver) Start() (errs []error) {
 	value := 0
 	go func() {
+		timer := time.NewTimer(a.interval)
+		timer.Stop()
 		for {
 			newValue, err := a.Read()
 			if err != nil {
@@ -66,9 +68,12 @@ func (a *AnalogSensorDriver) Start() (errs []error) {
 				value = newValue
 				a.Publish(a.Event(Data), value)
 			}
+
+			timer.Reset(a.interval)
 			select {
-			case <-time.After(a.interval):
+			case <-timer.C:
 			case <-a.halt:
+				timer.Stop()
 				return
 			}
 		}

drivers/gpio/analog_sensor_driver_test.go

@@ -14,8 +14,11 @@ var _ gobot.Driver = (*AnalogSensorDriver)(nil)
 func TestAnalogSensorDriver(t *testing.T) {
 	d := NewAnalogSensorDriver(newGpioTestAdaptor(), "1")
 	gobottest.Refute(t, d.Connection(), nil)
+	// default interval
+	gobottest.Assert(t, d.interval, 10*time.Millisecond)
 
-	d = NewAnalogSensorDriver(newGpioTestAdaptor(), "1", 30*time.Second)
+	d = NewAnalogSensorDriver(newGpioTestAdaptor(), "42", 30*time.Second)
+	gobottest.Assert(t, d.Pin(), "42")
 	gobottest.Assert(t, d.interval, 30*time.Second)
 
 	testAdaptorAnalogRead = func() (val int, err error) {
@@ -33,18 +36,15 @@ func TestAnalogSensorDriverStart(t *testing.T) {
 
 	d := NewAnalogSensorDriver(newGpioTestAdaptor(), "1")
 
-	testAdaptorAnalogRead = func() (val int, err error) {
-		val = 0
-		return
-	}
 	gobottest.Assert(t, len(d.Start()), 0)
 
-	// data was received
+	// expect data to be received
 	d.Once(d.Event(Data), func(data interface{}) {
 		gobottest.Assert(t, data.(int), 100)
 		sem <- true
 	})
 
+	// send data
 	testAdaptorAnalogRead = func() (val int, err error) {
 		val = 100
 		return
@@ -56,12 +56,13 @@ func TestAnalogSensorDriverStart(t *testing.T) {
 		t.Errorf("AnalogSensor Event \"Data\" was not published")
 	}
 
-	// read error
+	// expect error to be received
 	d.Once(d.Event(Error), func(data interface{}) {
 		gobottest.Assert(t, data.(error).Error(), "read error")
 		sem <- true
 	})
 
+	// send error
 	testAdaptorAnalogRead = func() (val int, err error) {
 		err = errors.New("read error")
 		return