clockwork

README

clockwork

a simple fake clock for golang

Usage

Replace uses of the time package with the clockwork.Clock interface instead.

For example, instead of using time.Sleep directly:

func myFunc() {
	time.Sleep(3 * time.Second)
	doSomething()
}

inject a clock and use its Sleep method instead:

func myFunc(clock clockwork.Clock) {
	clock.Sleep(3 * time.Second)
	doSomething()
}

Now you can easily test myFunc with a FakeClock:

func TestMyFunc(t *testing.T) {
	c := clockwork.NewFakeClock()

	// Start our sleepy function
	var wg sync.WaitGroup
	wg.Add(1)
	go func() {
		myFunc(c)
		wg.Done()
	}()

	// Ensure we wait until myFunc is sleeping
	c.BlockUntil(1)

	assertState()

	// Advance the FakeClock forward in time
	c.Advance(3 * time.Second)

	// Wait until the function completes
	wg.Wait()

	assertState()
}

and in production builds, simply inject the real clock instead:

myFunc(clockwork.NewRealClock())

See example_test.go for a full example.

Credits

clockwork is inspired by @wickman's threaded fake clock, and the Golang playground

Documentation

Index

• type Clock
  • func NewRealClock() Clock
• type FakeClock
  • func NewFakeClock() FakeClock
  • func NewFakeClockAt(t time.Time) FakeClock
• type Ticker

Types

type Clock

type Clock interface {
	After(d time.Duration) <-chan time.Time
	At(t time.Time) <-chan time.Time

	Sleep(d time.Duration)
	Now() time.Time
	Since(t time.Time) time.Duration
	NewTicker(d time.Duration) Ticker
}

Clock provides an interface that packages can use instead of directly using the time module, so that chronology-related behavior can be tested

func NewRealClock

func NewRealClock() Clock

NewRealClock returns a Clock which simply delegates calls to the actual time package; it should be used by packages in production.

type FakeClock

type FakeClock interface {
	Clock
	// Advance advances the FakeClock to a new point in time, ensuring any existing
	// sleepers are notified appropriately before returning
	Advance(d time.Duration)

	// AdvanceTo advances the FakeClock to a new point in time, where the time
	// is specified directly. Returns false if the specified time has allready
	// passed.
	AdvanceTo(t time.Time) bool

	// NextWakeup returns the earliest time from now that a blocker would
	// wait up. Returns a Zero time if there are no more blockers.
	//
	// This can be used with Advance to wake subsequent blockers no matter
	// what time they are blocked on.
	NextWakeup() time.Time

	// BlockUntil will block until the FakeClock has the given number of
	// sleepers (callers of Sleep or After)
	BlockUntil(n int)

	// NumSleepCalls returns the number of calls to a blocking sleep function
	// (Sleep and After).
	NumSleepCalls() int64
}

FakeClock provides an interface for a clock which can be manually advanced through time

func NewFakeClock

func NewFakeClock() FakeClock

NewFakeClock returns a FakeClock implementation which can be manually advanced through time for testing. The initial time of the FakeClock will be an arbitrary non-zero time.

func NewFakeClockAt

func NewFakeClockAt(t time.Time) FakeClock

NewFakeClockAt returns a FakeClock initialised at the given time.Time.

type Ticker

type Ticker interface {
	Chan() <-chan time.Time
	Stop()
}

Ticker provides an interface which can be used instead of directly using the ticker within the time module. The real-time ticker t provides ticks through t.C which becomes now t.Chan() to make this channel requirement definable in this interface.