clockwork

A simple fake clock for Go.

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) {
	ctx := context.Background()
	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 waiting on the clock.
	// Use a context to avoid blocking forever if something
	// goes wrong.
	ctx, cancel := context.WithTimeout(ctx, 10*time.Second)
	defer cancel()
	c.BlockUntilContext(ctx, 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

License

Apache License, Version 2.0. Please see License File for more information.