Add context-aware "time" library wrapper.

go/src/infra/libs/clock/duration_test.go

+// Copyright (c) 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 clock
+
+import (
+        "encoding/json"
+        "flag"
+        "testing"
+        "time"
+
+        . "github.com/smartystreets/goconvey/convey"
+)
+
+func TestDuration(t *testing.T) {
+        Convey(`A DurationFlag flag`, t, func() {
+                fs := flag.NewFlagSet("test", flag.ContinueOnError)
+                var d DurationFlag
+                fs.Var(&d, "duration", "Test duration parameter.")
+
+                Convey(`Parses a 10-second Duration from "10s".`, func() {
+                        err := fs.Parse([]string{"-duration", "10s"})
+                        So(err, ShouldBeNil)
+                        So(d.Duration(), ShouldEqual, time.Second*10)
+                        So(d.IsZero(), ShouldBeFalse)
+                })
+
+                Convey(`Returns an error when parsing "10z".`, func() {
+                        err := fs.Parse([]string{"-duration", "10z"})
+                        So(err, ShouldNotBeNil)
+                })
+
+                Convey(`When treated as a JSON field`, func() {
+                        var s struct {
+                                D DurationFlag `json:"duration"`
+                        }
+
+                        testJSON := `{"duration":10}`
+                        Convey(`Fails to unmarshal from `+testJSON+`.`, func() {
+                                testJSON := testJSON
+                                err := json.Unmarshal([]byte(testJSON), &s)
+                                So(err, ShouldNotBeNil)
+                        })
+
+                        Convey(`Marshals correctly to duration string.`, func() {
+                                testDuration := (5 * time.Second) + (2 * time.Minute)
+                                s.D = DurationFlag(testDuration)
+                                testJSON, err := json.Marshal(&s)
+                                So(err, ShouldBeNil)
+                                So(string(testJSON), ShouldEqual, `{"duration":"2m5s"}`)
+
+                                Convey(`And Unmarshals correctly.`, func() {
+                                        s.D = DurationFlag(0)
+                                        err := json.Unmarshal([]byte(testJSON), &s)
+                                        So(err, ShouldBeNil)
+                                        So(s.D.Duration(), ShouldEqual, testDuration)
+                                })
+                        })
+                })
+        })
+}