Add time2 package with time freeze feature

time2/const.go

@@ -0,0 +1,16 @@
+package time2
+
+import (
+	"time"
+)
+
+const (
+	// Day is a 24 hour long duration.
+	Day = 24 * time.Hour
+	// Week is a 7 days long duration.
+	Week = 7 * Day
+	// Month is a 30 days long duration.
+	Month = 30 * Day
+	// Year is a 365 days long duration.
+	Year = 365 * Day
+)

time2/stop.go

@@ -0,0 +1,71 @@
+package time2
+
+import (
+	"sync"
+	"time"
+)
+
+var (
+	stopMux    sync.RWMutex
+	stoppedFor time.Duration
+	stoppedAt  *time.Time
+
+	// Now returns current time. For testing aid it could be replaced with a
+	// stoppable implementation.
+	Now = time.Now
+)
+
+// InstrumentNow extends the package with a testing suitable implementation of
+// the Now function. This function is supposed to be called at the beginning of
+// a test suite.
+func InstrumentNow() {
+	Now = stoppableNow
+}
+
+// RestoreNow resets Now implementaion to the one from standard library. I have
+// no clue if it's going to be useful or not.
+func RestoreNow() {
+	Now = time.Now
+}
+
+// stoppableNow returns current time taking time manipulation into account.
+func stoppableNow() time.Time {
+	stopMux.RLock()
+	defer stopMux.RUnlock()
+
+	if stoppedAt != nil {
+		return *stoppedAt
+	}
+	return time.Now().Add(-stoppedFor)
+}
+
+// Stop makes the time stop.
+func Stop() {
+	stopMux.Lock()
+	if stoppedAt != nil {
+		panic("Time was already stopped")
+	}
+	now := Now()
+	stoppedAt = &now
+	stopMux.Unlock()
+}
+
+// Resume makes the time go again.
+func Resume() {
+	stopMux.Lock()
+	if stoppedAt == nil {
+		panic("Time was not stopped")
+	}
+	stoppedFor += time.Since(*stoppedAt)
+	stoppedAt = nil
+	stopMux.Unlock()
+}
+
+// Reset makes it appear like time was never been frozen. Call this function
+// at the beginning of every test case.
+func Reset() {
+	stopMux.Lock()
+	stoppedAt = nil
+	stoppedFor = 0
+	stopMux.Unlock()
+}