Add context-aware "time" library wrapper.

go/src/infra/libs/clock/testclock/testclock_test.go

+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package testclock
+
+import (
+        "testing"
+        "time"
+
+        . "github.com/smartystreets/goconvey/convey"
+        "infra/libs/clock"
+)
+
+func TestTestClock(t *testing.T) {
+        Convey(`A testing clock instance`, t, func() {
+                now := time.Date(2015, 01, 01, 00, 00, 00, 00, time.UTC)
+                c := New(now)
+
+                Convey(`Returns the current time.`, func() {
+                        So(c.Now(), ShouldResemble, now)
+                })
+
+                Convey(`When sleeping with a time of zero, immediately awakens.`, func() {
+                        c.Sleep(0)
+                        So(c.Now(), ShouldResemble, now)
+                })
+
+                Convey(`When sleeping for a period of time, awakens when signalled.`, func() {
+                        sleepingC := make(chan struct{})
+                        c.SetTimerCallback(func(_ clock.Timer) {
+                                close(sleepingC)
+                        })
+
+                        awakeC := make(chan time.Time)
+                        go func() {
+                                c.Sleep(2 * time.Second)
+                                awakeC <- c.Now()
+                        }()
+
+                        <-sleepingC
+                        c.Set(now.Add(1 * time.Second))
+                        c.Set(now.Add(2 * time.Second))
+                        So(<-awakeC, ShouldResemble, now.Add(2*time.Second))
+                })
+
+                Convey(`Awakens after a period of time.`, func() {
+                        afterC := c.After(2 * time.Second)
+                        awakeC := make(chan time.Time)
+                        go func() {
+                                awakeC <- <-afterC

[iannucci, 2015/06/03 17:37:20]

well that's a very odd construction... why not just wait on afterC?

[dnj, 2015/06/03 18:21:27]

Heh no idea.

+                        }()
+
+                        c.Set(now.Add(1 * time.Second))
+                        c.Set(now.Add(2 * time.Second))
+                        So(<-awakeC, ShouldResemble, now.Add(2*time.Second))
+                })
+        })
+}