Implement AfterFunc for Clock, FakeClock and IntervalClock and add un…

…it tests for the same

Signed-off-by: Madhav Jivrajani <madhav.jiv@gmail.com>

clock/clock.go

@@ -36,6 +36,9 @@ type Clock interface {
 	After(d time.Duration) <-chan time.Time
 	// NewTimer returns a new Timer.
 	NewTimer(d time.Duration) Timer
+	// AfterFunc executes f in its own goroutine after waiting for d duration and returns
+	// a Timer whose channel can be closed by calling Stop() on the Timer.
+	AfterFunc(d time.Duration, f func()) Timer
 	// Sleep sleeps for the provided duration d.
 	// Consider making the sleep interruptible by using 'select' on a context channel and a timer channel.
 	Sleep(d time.Duration)
@@ -88,6 +91,13 @@ func (RealClock) NewTimer(d time.Duration) Timer {
 	}
 }
 
+// AfterFunc is the same as time.AfterFunc(d, f).
+func (RealClock) AfterFunc(d time.Duration, f func()) Timer {
+	return &realTimer{
+		timer: time.AfterFunc(d, f),
+	}
+}
+
 // Tick is the same as time.Tick(d)
 // This method does not allow to free/GC the backing ticker. Use
 // NewTicker instead.

clock/testing/fake_clock.go

@@ -49,6 +49,7 @@ type fakeClockWaiter struct {
 	skipIfBlocked bool
 	destChan      chan time.Time
 	fired         bool
+	afterFunc     func()
 }
 
 // NewFakePassiveClock returns a new FakePassiveClock.
@@ -116,6 +117,25 @@ func (f *FakeClock) NewTimer(d time.Duration) clock.Timer {
 	return timer
 }
 
+// AfterFunc is the Fake version of time.AfterFunc(d, cb).
+func (f *FakeClock) AfterFunc(d time.Duration, cb func()) clock.Timer {
+	f.lock.Lock()
+	defer f.lock.Unlock()
+	stopTime := f.time.Add(d)
+	ch := make(chan time.Time, 1) // Don't block!
+
+	timer := &fakeTimer{
+		fakeClock: f,
+		waiter: fakeClockWaiter{
+			targetTime: stopTime,
+			destChan:   ch,
+			afterFunc:  cb,
+		},
+	}
+	f.waiters = append(f.waiters, &timer.waiter)
+	return timer
+}
+
 // Tick constructs a fake ticker, akin to time.Tick
 func (f *FakeClock) Tick(d time.Duration) <-chan time.Time {
 	if d <= 0 {
@@ -175,7 +195,6 @@ func (f *FakeClock) setTimeLocked(t time.Time) {
 	for i := range f.waiters {
 		w := f.waiters[i]
 		if !w.targetTime.After(t) {
-
 			if w.skipIfBlocked {
 				select {
 				case w.destChan <- t:
@@ -187,6 +206,10 @@ func (f *FakeClock) setTimeLocked(t time.Time) {
 				w.fired = true
 			}
 
+			if w.afterFunc != nil {
+				w.afterFunc()
+			}
+
 			if w.stepInterval > 0 {
 				for !w.targetTime.After(t) {
 					w.targetTime = w.targetTime.Add(w.stepInterval)
@@ -201,7 +224,7 @@ func (f *FakeClock) setTimeLocked(t time.Time) {
 	f.waiters = newWaiters
 }
 
-// HasWaiters returns true if After has been called on f but not yet satisfied (so you can
+// HasWaiters returns true if After or AfterFunc has been called on f but not yet satisfied (so you can
 // write race-free tests).
 func (f *FakeClock) HasWaiters() bool {
 	f.lock.RLock()
@@ -245,6 +268,12 @@ func (*IntervalClock) NewTimer(d time.Duration) clock.Timer {
 	panic("IntervalClock doesn't implement NewTimer")
 }
 
+// AfterFunc is unimplemented, will panic.
+// TODO: make interval clock use FakeClock so this can be implemented.
+func (*IntervalClock) AfterFunc(d time.Duration, f func()) clock.Timer {
+	panic("IntervalClock doesn't implement AfterFunc")
+}
+
 // Tick is unimplemented, will panic.
 // TODO: make interval clock use FakeClock so this can be implemented.
 func (*IntervalClock) Tick(d time.Duration) <-chan time.Time {

clock/testing/fake_clock_test.go

@@ -137,6 +137,66 @@ func TestFakeAfter(t *testing.T) {
 	}
 }
 
+func TestFakeAfterFunc(t *testing.T) {
+	tc := NewFakeClock(time.Now())
+	if tc.HasWaiters() {
+		t.Errorf("unexpected waiter?")
+	}
+	expectOneSecTimerFire := false
+	oneSecTimerFire := 0
+	tc.AfterFunc(time.Second, func() {
+		if !expectOneSecTimerFire {
+			t.Errorf("oneSecTimer func fired")
+		} else {
+			oneSecTimerFire++
+		}
+	})
+	if !tc.HasWaiters() {
+		t.Errorf("unexpected lack of waiter?")
+	}
+
+	expectOneOhOneSecTimerFire := false
+	oneOhOneSecTimerFire := 0
+	tc.AfterFunc(time.Second+time.Millisecond, func() {
+		if !expectOneOhOneSecTimerFire {
+			t.Errorf("oneOhOneSecTimer func fired")
+		} else {
+			oneOhOneSecTimerFire++
+		}
+	})
+
+	expectTwoSecTimerFire := false
+	twoSecTimerFire := 0
+	twoSecTimer := tc.AfterFunc(2*time.Second, func() {
+		if !expectTwoSecTimerFire {
+			t.Errorf("twoSecTimer func fired")
+		} else {
+			twoSecTimerFire++
+		}
+	})
+
+	tc.Step(999 * time.Millisecond)
+
+	expectOneSecTimerFire = true
+	tc.Step(time.Millisecond)
+	if oneSecTimerFire != 1 {
+		t.Errorf("expected oneSecTimerFire=1, got %d", oneSecTimerFire)
+	}
+	expectOneSecTimerFire = false
+
+	expectOneOhOneSecTimerFire = true
+	tc.Step(time.Millisecond)
+	if oneOhOneSecTimerFire != 1 {
+		// should not double-trigger!
+		t.Errorf("expected oneOhOneSecTimerFire=1, got %d", oneOhOneSecTimerFire)
+	}
+	expectOneOhOneSecTimerFire = false
+
+	// ensure a canceled timer doesn't fire
+	twoSecTimer.Stop()
+	tc.Step(time.Second)
+}
+
 func TestFakeTick(t *testing.T) {
 	tc := NewFakeClock(time.Now())
 	if tc.HasWaiters() {