Add context-aware "time" library wrapper.

go/src/infra/libs/clock/clockflag/time_test.go

Index: go/src/infra/libs/clock/clockflag/time_test.go
diff --git a/go/src/infra/libs/clock/clockflag/time_test.go b/go/src/infra/libs/clock/clockflag/time_test.go
new file mode 100644
index 0000000000000000000000000000000000000000..771c5cb31fdee4e753ac482ec3c48d21ed51fcfb
--- /dev/null
+++ b/go/src/infra/libs/clock/clockflag/time_test.go
@@ -0,0 +1,62 @@
+// 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 clockflag
+
+import (
+	"encoding/json"
+	"flag"
+	"testing"
+	"time"
+
+	. "github.com/smartystreets/goconvey/convey"
+)
+
+func TestTime(t *testing.T) {
+	t.Parallel()
+
+	Convey(`A Time flag`, t, func() {
+		fs := flag.NewFlagSet("test", flag.ContinueOnError)
+		var d Time
+		fs.Var(&d, "time", "Test time parameter.")
+
+		Convey(`Parses a 10-second Time from "2015-05-05T23:47:17+00:00".`, func() {
+			err := fs.Parse([]string{"-time", "2015-05-05T23:47:17+00:00"})
+			So(err, ShouldBeNil)
+			So(d.Time().Equal(time.Unix(1430869637, 0)), ShouldBeTrue)
+		})
+
+		Convey(`Returns an error when parsing "asdf".`, func() {
+			err := fs.Parse([]string{"-time", "asdf"})
+			So(err, ShouldNotBeNil)
+		})
+
+		Convey(`When treated as a JSON field`, func() {
+			var s struct {
+				T Time `json:"time"`
+			}
+
+			testJSON := `{"time":"asdf"}`
+			Convey(`Fails to unmarshal from `+testJSON+`.`, func() {
+				testJSON := testJSON
+				err := json.Unmarshal([]byte(testJSON), &s)
+				So(err, ShouldNotBeNil)
+			})
+
+			Convey(`Marshals correctly to RFC3339 time string.`, func() {
+				s.T = Time(time.Unix(1430869637, 0))
+				testJSON, err := json.Marshal(&s)
+				So(err, ShouldBeNil)
+				So(string(testJSON), ShouldEqual, `{"time":"2015-05-05T23:47:17Z"}`)
+
+				Convey(`And Unmarshals correctly.`, func() {
+					s.T = Time{}
+					err := json.Unmarshal([]byte(testJSON), &s)
+					So(err, ShouldBeNil)
+					So(s.T.Time().Equal(time.Unix(1430869637, 0)), ShouldBeTrue)
+				})
+			})
+		})
+	})
+}