diff --git a/LICENSE b/LICENSE
new file mode 100644
index 0000000..ce212cb
--- /dev/null
+++ b/LICENSE
@@ -0,0 +1,21 @@
+The MIT License (MIT)
+
+Copyright (c) 2014 Ben Johnson
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
diff --git a/README.md b/README.md
new file mode 100644
index 0000000..a3f2580
--- /dev/null
+++ b/README.md
@@ -0,0 +1,104 @@
+clock
+=====
+
+Clock is a small library for mocking time in Go. It provides an interface
+around the standard library's [`time`][time] package so that the application
+can use the realtime clock while tests can use the mock clock.
+
+[time]: http://golang.org/pkg/time/
+
+
+## Usage
+
+### Realtime Clock
+
+Your application can maintain a `Clock` variable that will allow realtime and
+mock clocks to be interchangable. For example, if you had an `Application` type:
+
+```go
+import "github.com/benbjohnson/clock"
+
+type Application struct {
+	Clock clock.Clock
+}
+```
+
+You could initialize it to use the realtime clock like this:
+
+```go
+var app Application
+app.Clock = clock.New()
+...
+```
+
+Then all timers and time-related functionality should be performed from the
+`Clock` variable.
+
+
+### Mocking time
+
+In your tests, you will want to use a `Mock` clock:
+
+```go
+import (
+	"testing"
+
+	"github.com/benbjohnson/clock"
+)
+
+func TestApplication_DoSomething(t *testing.T) {
+	mock := clock.NewMock()
+	app := Application{Clock: mock}
+	...
+}
+```
+
+Now that you've initialized your application to use the mock clock, you can
+adjust the time programmatically. The mock clock always starts from the Unix
+epoch (midnight, Jan 1, 1970 UTC).
+
+
+### Controlling time
+
+The mock clock provides the same functions that the standard library's `time`
+package provides. For example, to find the current time, you use the `Now()`
+function:
+
+```go
+mock := clock.NewMock()
+
+// Find the current time.
+mock.Now().UTC() // 1970-01-01 00:00:00 +0000 UTC
+
+// Move the clock forward.
+mock.Add(2 * time.Hour)
+
+// Check the time again. It's 2 hours later!
+mock.Now().UTC() // 1970-01-01 02:00:00 +0000 UTC
+```
+
+Timers and Tickers are also controlled by this same mock clock. They will only
+execute when the clock is moved forward:
+
+```
+mock := clock.NewMock()
+count := 0
+
+// Kick off a timer to increment every 1 mock second.
+go func() {
+    ticker := clock.Ticker(1 * time.Second)
+    for {
+        <-ticker.C
+        count++
+    }
+}()
+runtime.Gosched()
+
+// Move the clock forward 10 second.
+mock.Add(10 * time.Second)
+
+// This prints 10.
+fmt.Println(count)
+```
+
+
diff --git a/clock.go b/clock.go
new file mode 100644
index 0000000..cc109d4
--- /dev/null
+++ b/clock.go
@@ -0,0 +1,360 @@
+package clock
+
+import (
+	"sort"
+	"sync"
+	"time"
+)
+
+// Clock represents an interface to the functions in the standard library time
+// package. Two implementations are available in the clock package. The first
+// is a real-time clock which simply wraps the time package's functions. The
+// second is a mock clock which will only make forward progress when
+// programmatically adjusted.
+type Clock interface {
+	After(d time.Duration) <-chan time.Time
+	AfterFunc(d time.Duration, f func()) *Timer
+	Now() time.Time
+	Since(t time.Time) time.Duration
+	Sleep(d time.Duration)
+	Tick(d time.Duration) <-chan time.Time
+	Ticker(d time.Duration) *Ticker
+	Timer(d time.Duration) *Timer
+}
+
+// New returns an instance of a real-time clock.
+func New() Clock {
+	return &clock{}
+}
+
+// clock implements a real-time clock by simply wrapping the time package functions.
+type clock struct{}
+
+func (c *clock) After(d time.Duration) <-chan time.Time { return time.After(d) }
+
+func (c *clock) AfterFunc(d time.Duration, f func()) *Timer {
+	return &Timer{timer: time.AfterFunc(d, f)}
+}
+
+func (c *clock) Now() time.Time { return time.Now() }
+
+func (c *clock) Since(t time.Time) time.Duration { return time.Since(t) }
+
+func (c *clock) Sleep(d time.Duration) { time.Sleep(d) }
+
+func (c *clock) Tick(d time.Duration) <-chan time.Time { return time.Tick(d) }
+
+func (c *clock) Ticker(d time.Duration) *Ticker {
+	t := time.NewTicker(d)
+	return &Ticker{C: t.C, ticker: t}
+}
+
+func (c *clock) Timer(d time.Duration) *Timer {
+	t := time.NewTimer(d)
+	return &Timer{C: t.C, timer: t}
+}
+
+// Mock represents a mock clock that only moves forward programmically.
+// It can be preferable to a real-time clock when testing time-based functionality.
+type Mock struct {
+	mu      sync.Mutex
+	now     time.Time   // current time
+	timers  clockTimers // tickers & timers
+	gosched func()
+}
+
+type MockOpt struct {
+	// Gosched is a function which is called to schedule other (app-specific)
+	// goroutines. Default implementation just sleeps for 1 millisecond. It is
+	// often not acceptable because it slows down tests significantly and is also
+	// potentialy fragile.
+	Gosched func()
+}
+
+// NewMock returns an instance of a mock clock with the default options.
+// See also NewMockOpt
+func NewMock() *Mock {
+	return NewMockOpt(MockOpt{})
+}
+
+// NewMockOpt returns an instance of a mock clock.
+// The current time of the mock clock on initialization is the Unix epoch.
+// See MockOpt for description of available options.
+func NewMockOpt(opt MockOpt) *Mock {
+	mock := &Mock{
+		now:     time.Unix(0, 0),
+		gosched: opt.Gosched,
+	}
+	if mock.gosched == nil {
+		mock.gosched = func() {
+			time.Sleep(1 * time.Millisecond)
+		}
+	}
+
+	return mock
+}
+
+// Add moves the current time of the mock clock forward by the duration.
+// This should only be called from a single goroutine at a time.
+func (m *Mock) Add(d time.Duration) {
+	// Calculate the final current time.
+	t := m.now.Add(d)
+
+	// Continue to execute timers until there are no more before the new time.
+	for {
+		if !m.runNextTimer(t) {
+			break
+		}
+	}
+
+	// Ensure that we end with the new time.
+	m.mu.Lock()
+	m.now = t
+	m.mu.Unlock()
+
+	// Give a small buffer to make sure the other goroutines get handled.
+	m.gosched()
+}
+
+// Set sets the current time of the mock clock to a specific one.
+// This should only be called from a single goroutine at a time.
+func (m *Mock) Set(t time.Time) {
+	// Continue to execute timers until there are no more before the new time.
+	for {
+		if !m.runNextTimer(t) {
+			break
+		}
+	}
+
+	// Ensure that we end with the new time.
+	m.mu.Lock()
+	m.now = t
+	m.mu.Unlock()
+
+	// Give a small buffer to make sure the other goroutines get handled.
+	m.gosched()
+}
+
+// runNextTimer executes the next timer in chronological order and moves the
+// current time to the timer's next tick time. The next time is not executed if
+// it's next time if after the max time. Returns true if a timer is executed.
+func (m *Mock) runNextTimer(max time.Time) bool {
+	m.mu.Lock()
+
+	// Sort timers by time.
+	sort.Sort(m.timers)
+
+	// If we have no more timers then exit.
+	if len(m.timers) == 0 {
+		m.mu.Unlock()
+		return false
+	}
+
+	// Retrieve next timer. Exit if next tick is after new time.
+	t := m.timers[0]
+	if t.Next().After(max) {
+		m.mu.Unlock()
+		return false
+	}
+
+	// Move "now" forward and unlock clock.
+	m.now = t.Next()
+	m.mu.Unlock()
+
+	// Execute timer.
+	t.Tick(m.now)
+	return true
+}
+
+// After waits for the duration to elapse and then sends the current time on the returned channel.
+func (m *Mock) After(d time.Duration) <-chan time.Time {
+	return m.Timer(d).C
+}
+
+// AfterFunc waits for the duration to elapse and then executes a function.
+// A Timer is returned that can be stopped.
+func (m *Mock) AfterFunc(d time.Duration, f func()) *Timer {
+	t := m.Timer(d)
+	t.C = nil
+	t.fn = f
+	return t
+}
+
+// Now returns the current wall time on the mock clock.
+func (m *Mock) Now() time.Time {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	return m.now
+}
+
+// Since returns time since the mock clocks wall time.
+func (m *Mock) Since(t time.Time) time.Duration {
+	return m.Now().Sub(t)
+}
+
+// Sleep pauses the goroutine for the given duration on the mock clock.
+// The clock must be moved forward in a separate goroutine.
+func (m *Mock) Sleep(d time.Duration) {
+	<-m.After(d)
+}
+
+// Tick is a convenience function for Ticker().
+// It will return a ticker channel that cannot be stopped.
+func (m *Mock) Tick(d time.Duration) <-chan time.Time {
+	return m.Ticker(d).C
+}
+
+// Ticker creates a new instance of Ticker.
+func (m *Mock) Ticker(d time.Duration) *Ticker {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	ch := make(chan time.Time, 1)
+	t := &Ticker{
+		C:    ch,
+		c:    ch,
+		mock: m,
+		d:    d,
+		next: m.now.Add(d),
+	}
+	m.timers = append(m.timers, (*internalTicker)(t))
+	return t
+}
+
+// Timer creates a new instance of Timer.
+func (m *Mock) Timer(d time.Duration) *Timer {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	ch := make(chan time.Time, 1)
+	t := &Timer{
+		C:       ch,
+		c:       ch,
+		mock:    m,
+		next:    m.now.Add(d),
+		stopped: false,
+	}
+	m.timers = append(m.timers, (*internalTimer)(t))
+	return t
+}
+
+func (m *Mock) removeClockTimer(t clockTimer) {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	for i, timer := range m.timers {
+		if timer == t {
+			copy(m.timers[i:], m.timers[i+1:])
+			m.timers[len(m.timers)-1] = nil
+			m.timers = m.timers[:len(m.timers)-1]
+			break
+		}
+	}
+	sort.Sort(m.timers)
+}
+
+// clockTimer represents an object with an associated start time.
+type clockTimer interface {
+	Next() time.Time
+	Tick(time.Time)
+}
+
+// clockTimers represents a list of sortable timers.
+type clockTimers []clockTimer
+
+func (a clockTimers) Len() int           { return len(a) }
+func (a clockTimers) Swap(i, j int)      { a[i], a[j] = a[j], a[i] }
+func (a clockTimers) Less(i, j int) bool { return a[i].Next().Before(a[j].Next()) }
+
+// Timer represents a single event.
+// The current time will be sent on C, unless the timer was created by AfterFunc.
+type Timer struct {
+	C       <-chan time.Time
+	c       chan time.Time
+	timer   *time.Timer // realtime impl, if set
+	next    time.Time   // next tick time
+	mock    *Mock       // mock clock, if set
+	fn      func()      // AfterFunc function, if set
+	stopped bool        // True if stopped, false if running
+}
+
+// Stop turns off the ticker.
+func (t *Timer) Stop() bool {
+	if t.timer != nil {
+		return t.timer.Stop()
+	}
+
+	t.mock.mu.Lock()
+	registered := !t.stopped
+	t.mock.mu.Unlock()
+
+	t.mock.removeClockTimer((*internalTimer)(t))
+	t.mock.mu.Lock()
+	defer t.mock.mu.Unlock()
+	t.stopped = true
+	return registered
+}
+
+// Reset changes the expiry time of the timer
+func (t *Timer) Reset(d time.Duration) bool {
+	if t.timer != nil {
+		return t.timer.Reset(d)
+	}
+
+	t.next = t.mock.now.Add(d)
+	t.mock.mu.Lock()
+	defer t.mock.mu.Unlock()
+
+	registered := !t.stopped
+	if t.stopped {
+		t.mock.timers = append(t.mock.timers, (*internalTimer)(t))
+	}
+
+	t.stopped = false
+	return registered
+}
+
+type internalTimer Timer
+
+func (t *internalTimer) Next() time.Time { return t.next }
+func (t *internalTimer) Tick(now time.Time) {
+	if t.fn != nil {
+		t.fn()
+	} else {
+		t.c <- now
+	}
+	t.mock.removeClockTimer((*internalTimer)(t))
+	t.mock.mu.Lock()
+	defer t.mock.mu.Unlock()
+
+	t.stopped = true
+	t.mock.gosched()
+}
+
+// Ticker holds a channel that receives "ticks" at regular intervals.
+type Ticker struct {
+	C      <-chan time.Time
+	c      chan time.Time
+	ticker *time.Ticker  // realtime impl, if set
+	next   time.Time     // next tick time
+	mock   *Mock         // mock clock, if set
+	d      time.Duration // time between ticks
+}
+
+// Stop turns off the ticker.
+func (t *Ticker) Stop() {
+	if t.ticker != nil {
+		t.ticker.Stop()
+	} else {
+		t.mock.removeClockTimer((*internalTicker)(t))
+	}
+}
+
+type internalTicker Ticker
+
+func (t *internalTicker) Next() time.Time { return t.next }
+func (t *internalTicker) Tick(now time.Time) {
+	select {
+	case t.c <- now:
+	default:
+	}
+	t.next = now.Add(t.d)
+	t.mock.gosched()
+}
diff --git a/clock_test.go b/clock_test.go
new file mode 100644
index 0000000..322b742
--- /dev/null
+++ b/clock_test.go
@@ -0,0 +1,599 @@
+package clock
+
+import (
+	"fmt"
+	"os"
+	"sync"
+	"sync/atomic"
+	"testing"
+	"time"
+)
+
+// Ensure that the clock's After channel sends at the correct time.
+func TestClock_After(t *testing.T) {
+	var ok bool
+	go func() {
+		time.Sleep(10 * time.Millisecond)
+		ok = true
+	}()
+	go func() {
+		time.Sleep(30 * time.Millisecond)
+		t.Fatal("too late")
+	}()
+	gosched()
+
+	<-New().After(20 * time.Millisecond)
+	if !ok {
+		t.Fatal("too early")
+	}
+}
+
+// Ensure that the clock's AfterFunc executes at the correct time.
+func TestClock_AfterFunc(t *testing.T) {
+	var ok bool
+	go func() {
+		time.Sleep(10 * time.Millisecond)
+		ok = true
+	}()
+	go func() {
+		time.Sleep(30 * time.Millisecond)
+		t.Fatal("too late")
+	}()
+	gosched()
+
+	var wg sync.WaitGroup
+	wg.Add(1)
+	New().AfterFunc(20*time.Millisecond, func() {
+		wg.Done()
+	})
+	wg.Wait()
+	if !ok {
+		t.Fatal("too early")
+	}
+}
+
+// Ensure that the clock's time matches the standary library.
+func TestClock_Now(t *testing.T) {
+	a := time.Now().Round(time.Second)
+	b := New().Now().Round(time.Second)
+	if !a.Equal(b) {
+		t.Errorf("not equal: %s != %s", a, b)
+	}
+}
+
+// Ensure that the clock sleeps for the appropriate amount of time.
+func TestClock_Sleep(t *testing.T) {
+	var ok bool
+	go func() {
+		time.Sleep(10 * time.Millisecond)
+		ok = true
+	}()
+	go func() {
+		time.Sleep(30 * time.Millisecond)
+		t.Fatal("too late")
+	}()
+	gosched()
+
+	New().Sleep(20 * time.Millisecond)
+	if !ok {
+		t.Fatal("too early")
+	}
+}
+
+// Ensure that the clock ticks correctly.
+func TestClock_Tick(t *testing.T) {
+	var ok bool
+	go func() {
+		time.Sleep(10 * time.Millisecond)
+		ok = true
+	}()
+	go func() {
+		time.Sleep(50 * time.Millisecond)
+		t.Fatal("too late")
+	}()
+	gosched()
+
+	c := New().Tick(20 * time.Millisecond)
+	<-c
+	<-c
+	if !ok {
+		t.Fatal("too early")
+	}
+}
+
+// Ensure that the clock's ticker ticks correctly.
+func TestClock_Ticker(t *testing.T) {
+	var ok bool
+	go func() {
+		time.Sleep(100 * time.Millisecond)
+		ok = true
+	}()
+	go func() {
+		time.Sleep(200 * time.Millisecond)
+		t.Fatal("too late")
+	}()
+	gosched()
+
+	ticker := New().Ticker(50 * time.Millisecond)
+	<-ticker.C
+	<-ticker.C
+	if !ok {
+		t.Fatal("too early")
+	}
+}
+
+// Ensure that the clock's ticker can stop correctly.
+func TestClock_Ticker_Stp(t *testing.T) {
+	var ok bool
+	go func() {
+		time.Sleep(10 * time.Millisecond)
+		ok = true
+	}()
+	gosched()
+
+	ticker := New().Ticker(20 * time.Millisecond)
+	<-ticker.C
+	ticker.Stop()
+	select {
+	case <-ticker.C:
+		t.Fatal("unexpected send")
+	case <-time.After(30 * time.Millisecond):
+	}
+}
+
+// Ensure that the clock's timer waits correctly.
+func TestClock_Timer(t *testing.T) {
+	var ok bool
+	go func() {
+		time.Sleep(10 * time.Millisecond)
+		ok = true
+	}()
+	go func() {
+		time.Sleep(30 * time.Millisecond)
+		t.Fatal("too late")
+	}()
+	gosched()
+
+	timer := New().Timer(20 * time.Millisecond)
+	<-timer.C
+	if !ok {
+		t.Fatal("too early")
+	}
+
+	if timer.Stop() {
+		t.Fatal("timer still running")
+	}
+}
+
+// Ensure that the clock's timer can be stopped.
+func TestClock_Timer_Stop(t *testing.T) {
+	var ok bool
+	go func() {
+		time.Sleep(10 * time.Millisecond)
+		ok = true
+	}()
+
+	timer := New().Timer(20 * time.Millisecond)
+	if !timer.Stop() {
+		t.Fatal("timer not running")
+	}
+	if timer.Stop() {
+		t.Fatal("timer wasn't cancelled")
+	}
+	select {
+	case <-timer.C:
+		t.Fatal("unexpected send")
+	case <-time.After(30 * time.Millisecond):
+	}
+}
+
+// Ensure that the clock's timer can be reset.
+func TestClock_Timer_Reset(t *testing.T) {
+	var ok bool
+	go func() {
+		time.Sleep(20 * time.Millisecond)
+		ok = true
+	}()
+	go func() {
+		time.Sleep(30 * time.Millisecond)
+		t.Fatal("too late")
+	}()
+	gosched()
+
+	timer := New().Timer(10 * time.Millisecond)
+	if !timer.Reset(20 * time.Millisecond) {
+		t.Fatal("timer not running")
+	}
+
+	<-timer.C
+	if !ok {
+		t.Fatal("too early")
+	}
+}
+
+// Ensure that the mock's After channel sends at the correct time.
+func TestMock_After(t *testing.T) {
+	var ok int32
+	clock := NewMock()
+
+	// Create a channel to execute after 10 mock seconds.
+	ch := clock.After(10 * time.Second)
+	go func(ch <-chan time.Time) {
+		<-ch
+		atomic.StoreInt32(&ok, 1)
+	}(ch)
+
+	// Move clock forward to just before the time.
+	clock.Add(9 * time.Second)
+	if atomic.LoadInt32(&ok) == 1 {
+		t.Fatal("too early")
+	}
+
+	// Move clock forward to the after channel's time.
+	clock.Add(1 * time.Second)
+	if atomic.LoadInt32(&ok) == 0 {
+		t.Fatal("too late")
+	}
+}
+
+// Ensure that the mock's After channel doesn't block on write.
+func TestMock_UnusedAfter(t *testing.T) {
+	mock := NewMock()
+	mock.After(1 * time.Millisecond)
+
+	done := make(chan bool, 1)
+	go func() {
+		mock.Add(1 * time.Second)
+		done <- true
+	}()
+
+	select {
+	case <-done:
+	case <-time.After(1 * time.Second):
+		t.Fatal("mock.Add hung")
+	}
+}
+
+// Ensure that the mock's AfterFunc executes at the correct time.
+func TestMock_AfterFunc(t *testing.T) {
+	var ok int32
+	clock := NewMock()
+
+	// Execute function after duration.
+	clock.AfterFunc(10*time.Second, func() {
+		atomic.StoreInt32(&ok, 1)
+	})
+
+	// Move clock forward to just before the time.
+	clock.Add(9 * time.Second)
+	if atomic.LoadInt32(&ok) == 1 {
+		t.Fatal("too early")
+	}
+
+	// Move clock forward to the after channel's time.
+	clock.Add(1 * time.Second)
+	if atomic.LoadInt32(&ok) == 0 {
+		t.Fatal("too late")
+	}
+}
+
+// Ensure that the mock's AfterFunc doesn't execute if stopped.
+func TestMock_AfterFunc_Stop(t *testing.T) {
+	// Execute function after duration.
+	clock := NewMock()
+	timer := clock.AfterFunc(10*time.Second, func() {
+		t.Fatal("unexpected function execution")
+	})
+	gosched()
+
+	// Stop timer & move clock forward.
+	timer.Stop()
+	clock.Add(10 * time.Second)
+	gosched()
+}
+
+// Ensure that the mock's current time can be changed.
+func TestMock_Now(t *testing.T) {
+	clock := NewMock()
+	if now := clock.Now(); !now.Equal(time.Unix(0, 0)) {
+		t.Fatalf("expected epoch, got: %v", now)
+	}
+
+	// Add 10 seconds and check the time.
+	clock.Add(10 * time.Second)
+	if now := clock.Now(); !now.Equal(time.Unix(10, 0)) {
+		t.Fatalf("expected epoch, got: %v", now)
+	}
+}
+
+func TestMock_Since(t *testing.T) {
+	clock := NewMock()
+
+	beginning := clock.Now()
+	clock.Add(500 * time.Second)
+	if since := clock.Since(beginning); since.Seconds() != 500 {
+		t.Fatalf("expected 500 since beginning, actually: %v", since.Seconds())
+	}
+}
+
+// Ensure that the mock can sleep for the correct time.
+func TestMock_Sleep(t *testing.T) {
+	var ok int32
+	clock := NewMock()
+
+	// Create a channel to execute after 10 mock seconds.
+	go func() {
+		clock.Sleep(10 * time.Second)
+		atomic.StoreInt32(&ok, 1)
+	}()
+	gosched()
+
+	// Move clock forward to just before the sleep duration.
+	clock.Add(9 * time.Second)
+	if atomic.LoadInt32(&ok) == 1 {
+		t.Fatal("too early")
+	}
+
+	// Move clock forward to the after the sleep duration.
+	clock.Add(1 * time.Second)
+	if atomic.LoadInt32(&ok) == 0 {
+		t.Fatal("too late")
+	}
+}
+
+// Ensure that the mock's Tick channel sends at the correct time.
+func TestMock_Tick(t *testing.T) {
+	var n int32
+	clock := NewMock()
+
+	// Create a channel to increment every 10 seconds.
+	go func() {
+		tick := clock.Tick(10 * time.Second)
+		for {
+			<-tick
+			atomic.AddInt32(&n, 1)
+		}
+	}()
+	gosched()
+
+	// Move clock forward to just before the first tick.
+	clock.Add(9 * time.Second)
+	if atomic.LoadInt32(&n) != 0 {
+		t.Fatalf("expected 0, got %d", n)
+	}
+
+	// Move clock forward to the start of the first tick.
+	clock.Add(1 * time.Second)
+	if atomic.LoadInt32(&n) != 1 {
+		t.Fatalf("expected 1, got %d", n)
+	}
+
+	// Move clock forward over several ticks.
+	clock.Add(30 * time.Second)
+	if atomic.LoadInt32(&n) != 4 {
+		t.Fatalf("expected 4, got %d", n)
+	}
+}
+
+// Ensure that the mock's Ticker channel sends at the correct time.
+func TestMock_Ticker(t *testing.T) {
+	var n int32
+	clock := NewMock()
+
+	// Create a channel to increment every microsecond.
+	go func() {
+		ticker := clock.Ticker(1 * time.Microsecond)
+		for {
+			<-ticker.C
+			atomic.AddInt32(&n, 1)
+		}
+	}()
+	gosched()
+
+	// Move clock forward.
+	clock.Add(10 * time.Microsecond)
+	if atomic.LoadInt32(&n) != 10 {
+		t.Fatalf("unexpected: %d", n)
+	}
+}
+
+// Ensure that the mock's Ticker channel won't block if not read from.
+func TestMock_Ticker_Overflow(t *testing.T) {
+	clock := NewMock()
+	ticker := clock.Ticker(1 * time.Microsecond)
+	clock.Add(10 * time.Microsecond)
+	ticker.Stop()
+}
+
+// Ensure that the mock's Ticker can be stopped.
+func TestMock_Ticker_Stop(t *testing.T) {
+	var n int32
+	clock := NewMock()
+
+	// Create a channel to increment every second.
+	ticker := clock.Ticker(1 * time.Second)
+	go func() {
+		for {
+			<-ticker.C
+			atomic.AddInt32(&n, 1)
+		}
+	}()
+	gosched()
+
+	// Move clock forward.
+	clock.Add(5 * time.Second)
+	if atomic.LoadInt32(&n) != 5 {
+		t.Fatalf("expected 5, got: %d", n)
+	}
+
+	ticker.Stop()
+
+	// Move clock forward again.
+	clock.Add(5 * time.Second)
+	if atomic.LoadInt32(&n) != 5 {
+		t.Fatalf("still expected 5, got: %d", n)
+	}
+}
+
+// Ensure that multiple tickers can be used together.
+func TestMock_Ticker_Multi(t *testing.T) {
+	var n int32
+	clock := NewMock()
+
+	go func() {
+		a := clock.Ticker(1 * time.Microsecond)
+		b := clock.Ticker(3 * time.Microsecond)
+
+		for {
+			select {
+			case <-a.C:
+				atomic.AddInt32(&n, 1)
+			case <-b.C:
+				atomic.AddInt32(&n, 100)
+			}
+		}
+	}()
+	gosched()
+
+	// Move clock forward.
+	clock.Add(10 * time.Microsecond)
+	gosched()
+	if atomic.LoadInt32(&n) != 310 {
+		t.Fatalf("unexpected: %d", n)
+	}
+}
+
+func ExampleMock_After() {
+	// Create a new mock clock.
+	clock := NewMock()
+	count := 0
+
+	ready := make(chan struct{})
+	// Create a channel to execute after 10 mock seconds.
+	go func() {
+		ch := clock.After(10 * time.Second)
+		close(ready)
+		<-ch
+		count = 100
+	}()
+	<-ready
+
+	// Print the starting value.
+	fmt.Printf("%s: %d\n", clock.Now().UTC(), count)
+
+	// Move the clock forward 5 seconds and print the value again.
+	clock.Add(5 * time.Second)
+	fmt.Printf("%s: %d\n", clock.Now().UTC(), count)
+
+	// Move the clock forward 5 seconds to the tick time and check the value.
+	clock.Add(5 * time.Second)
+	fmt.Printf("%s: %d\n", clock.Now().UTC(), count)
+
+	// Output:
+	// 1970-01-01 00:00:00 +0000 UTC: 0
+	// 1970-01-01 00:00:05 +0000 UTC: 0
+	// 1970-01-01 00:00:10 +0000 UTC: 100
+}
+
+func ExampleMock_AfterFunc() {
+	// Create a new mock clock.
+	clock := NewMock()
+	count := 0
+
+	// Execute a function after 10 mock seconds.
+	clock.AfterFunc(10*time.Second, func() {
+		count = 100
+	})
+	gosched()
+
+	// Print the starting value.
+	fmt.Printf("%s: %d\n", clock.Now().UTC(), count)
+
+	// Move the clock forward 10 seconds and print the new value.
+	clock.Add(10 * time.Second)
+	fmt.Printf("%s: %d\n", clock.Now().UTC(), count)
+
+	// Output:
+	// 1970-01-01 00:00:00 +0000 UTC: 0
+	// 1970-01-01 00:00:10 +0000 UTC: 100
+}
+
+func ExampleMock_Sleep() {
+	// Create a new mock clock.
+	clock := NewMock()
+	count := 0
+
+	// Execute a function after 10 mock seconds.
+	go func() {
+		clock.Sleep(10 * time.Second)
+		count = 100
+	}()
+	gosched()
+
+	// Print the starting value.
+	fmt.Printf("%s: %d\n", clock.Now().UTC(), count)
+
+	// Move the clock forward 10 seconds and print the new value.
+	clock.Add(10 * time.Second)
+	fmt.Printf("%s: %d\n", clock.Now().UTC(), count)
+
+	// Output:
+	// 1970-01-01 00:00:00 +0000 UTC: 0
+	// 1970-01-01 00:00:10 +0000 UTC: 100
+}
+
+func ExampleMock_Ticker() {
+	// Create a new mock clock.
+	clock := NewMock()
+	count := 0
+
+	ready := make(chan struct{})
+	// Increment count every mock second.
+	go func() {
+		ticker := clock.Ticker(1 * time.Second)
+		close(ready)
+		for {
+			<-ticker.C
+			count++
+		}
+	}()
+	<-ready
+
+	// Move the clock forward 10 seconds and print the new value.
+	clock.Add(10 * time.Second)
+	fmt.Printf("Count is %d after 10 seconds\n", count)
+
+	// Move the clock forward 5 more seconds and print the new value.
+	clock.Add(5 * time.Second)
+	fmt.Printf("Count is %d after 15 seconds\n", count)
+
+	// Output:
+	// Count is 10 after 10 seconds
+	// Count is 15 after 15 seconds
+}
+
+func ExampleMock_Timer() {
+	// Create a new mock clock.
+	clock := NewMock()
+	count := 0
+
+	ready := make(chan struct{})
+	// Increment count after a mock second.
+	go func() {
+		timer := clock.Timer(1 * time.Second)
+		close(ready)
+		<-timer.C
+		count++
+	}()
+	<-ready
+
+	// Move the clock forward 10 seconds and print the new value.
+	clock.Add(10 * time.Second)
+	fmt.Printf("Count is %d after 10 seconds\n", count)
+
+	// Output:
+	// Count is 1 after 10 seconds
+}
+
+func warn(v ...interface{})              { fmt.Fprintln(os.Stderr, v...) }
+func warnf(msg string, v ...interface{}) { fmt.Fprintf(os.Stderr, msg+"\n", v...) }
diff --git a/go.mod b/go.mod
new file mode 100644
index 0000000..9bf6444
--- /dev/null
+++ b/go.mod
@@ -0,0 +1,3 @@
+module github.com/dimonomid/clock
+
+go 1.13