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.