Add Context cancellation to clock.

common/clock/systemclock_test.go

+// Copyright 2016 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 clock
+
+import (
+        "testing"
+        "time"
+
+        "golang.org/x/net/context"
+
+        . "github.com/smartystreets/goconvey/convey"
+)
+
+// TestSystemClock tests the non-trivial system clock methods.
+func TestSystemClock(t *testing.T) {
+        t.Parallel()
+
+        Convey(`A cancelable Context`, t, func() {
+                c, cancelFunc := context.WithCancel(context.Background())
+                sc := GetSystemClock()
+
+                Convey(`Will perform a full sleep if the Context isn't canceled.`, func() {
+                        So(sc.Sleep(c, 100*time.Millisecond), ShouldBeNil)
+                })
+
+                Convey(`Will return Context error if canceled.`, func() {
+                        cancelFunc()
+                        So(sc.Sleep(c, 1*time.Hour), ShouldEqual, context.Canceled)
+                })
+
+                Convey(`Will terminate the Sleep prematurely if the Context is canceled.`, func() {
+                        cancelFunc()
+                        So(sc.Sleep(c, 1*time.Hour), ShouldEqual, context.Canceled)
+                })
+        })
+}