Replace ticker registrations when resetting and reject invalid periods

Author: ac1982

ticker.go

@@ -41,8 +41,12 @@ func newFakeTicker(fc *FakeClock, d time.Duration) *fakeTicker {
 		c: make(chan time.Time, 1),
 		d: d,
 		reset: func(d time.Duration) {
+			if d <= 0 {
+				panic("non-positive interval for Ticker.Reset")
+			}
 			fc.l.Lock()
 			defer fc.l.Unlock()
+			fc.stopExpirer(ft)
 			ft.d = d
 			fc.setExpirer(ft, d)
 		},

ticker_reset_test.go

@@ -0,0 +1,52 @@
+package clockwork
+
+import (
+	"testing"
+	"time"
+)
+
+func TestFakeTickerResetThenStop(t *testing.T) {
+	fc := NewFakeClock()
+	ticker := fc.NewTicker(time.Second)
+	ticker.Reset(2 * time.Second)
+	ticker.Reset(3 * time.Second)
+	ticker.Stop()
+	fc.Advance(10 * time.Second)
+	select {
+	case tick := <-ticker.Chan():
+		t.Fatalf("stopped ticker fired at %v after being reset", tick)
+	default:
+	}
+	ticker.Reset(2 * time.Second)
+	defer ticker.Stop()
+	fc.Advance(2 * time.Second)
+	select {
+	case <-ticker.Chan():
+	default:
+		t.Fatal("Reset did not restart the stopped ticker")
+	}
+}
+
+func TestFakeTickerResetNonPositive(t *testing.T) {
+	for _, duration := range []time.Duration{0, -time.Second} {
+		t.Run(duration.String(), func(t *testing.T) {
+			fc := NewFakeClock()
+			ticker := fc.NewTicker(time.Second)
+			defer ticker.Stop()
+			panicked := false
+			func() {
+				defer func() { panicked = recover() != nil }()
+				ticker.Reset(duration)
+			}()
+			if !panicked {
+				t.Fatal("Reset must panic for a non-positive duration")
+			}
+			fc.Advance(time.Second)
+			select {
+			case <-ticker.Chan():
+			default:
+				t.Fatal("invalid Reset changed the existing ticker schedule")
+			}
+		})
+	}
+}