cipd: Implement local cache for ResolveVersion(...) call with tags.

go/src/infra/tools/cipd/internal/checksum_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 internal
+
+import (
+        "testing"
+
+        "infra/tools/cipd/internal/messages"
+
+        . "github.com/smartystreets/goconvey/convey"
+)
+
+func TestChecksumCheckingWorks(t *testing.T) {
+        msg := messages.TagCache{
+                Entries: []*messages.TagCache_Entry{
+                        &messages.TagCache_Entry{
+                                Package:    strPtr("package"),
+                                Tag:        strPtr("tag"),
+                                InstanceId: strPtr("instance_id"),
+                        },
+                },
+        }
+
+        Convey("Works", t, func(c C) {
+                buf, err := MarshalWithSHA1(&msg)
+                So(err, ShouldBeNil)
+                out := messages.TagCache{}
+                So(UnmarshalWithSHA1(buf, &out), ShouldBeNil)
+                So(out, ShouldResemble, msg)
+        })
+
+        Convey("Rejects bad msg", t, func(c C) {
+                buf, err := MarshalWithSHA1(&msg)
+                So(err, ShouldBeNil)
+                buf[10] = 0
+                out := messages.TagCache{}
+                So(UnmarshalWithSHA1(buf, &out), ShouldNotBeNil)
+        })
+}
+
+func strPtr(s string) *string {
+        return &s
+}