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

go/src/infra/tools/cipd/internal/tagcache_test.go

Index: go/src/infra/tools/cipd/internal/tagcache_test.go
diff --git a/go/src/infra/tools/cipd/internal/tagcache_test.go b/go/src/infra/tools/cipd/internal/tagcache_test.go
new file mode 100644
index 0000000000000000000000000000000000000000..49232ff90ee9a2e39bb5aee2dd2a6832ac316cd2
--- /dev/null
+++ b/go/src/infra/tools/cipd/internal/tagcache_test.go
@@ -0,0 +1,54 @@
+// 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 (
+	"strings"
+	"testing"
+
+	. "github.com/smartystreets/goconvey/convey"
+	"infra/tools/cipd/common"
+)
+
+func TestTagCacheWorks(t *testing.T) {
+	Convey("Works", t, func(c C) {
+		tc := TagCache{}
+		So(tc.ResolveTag("pkg", "tag:1"), ShouldResemble, common.Pin{})
+		So(tc.Dirty(), ShouldBeFalse)
+
+		// Add new.
+		tc.AddTag(common.Pin{
+			PackageName: "pkg",
+			InstanceID:  strings.Repeat("a", 40),
+		}, "tag:1")
+		So(tc.Dirty(), ShouldBeTrue)
+		So(tc.ResolveTag("pkg", "tag:1"), ShouldResemble, common.Pin{
+			PackageName: "pkg",
+			InstanceID:  strings.Repeat("a", 40),
+		})
+
+		// Replace existing.
+		tc.AddTag(common.Pin{
+			PackageName: "pkg",
+			InstanceID:  strings.Repeat("b", 40),
+		}, "tag:1")
+		So(tc.Dirty(), ShouldBeTrue)
+		So(tc.ResolveTag("pkg", "tag:1"), ShouldResemble, common.Pin{
+			PackageName: "pkg",
+			InstanceID:  strings.Repeat("b", 40),
+		})
+
+		// Save\load.
+		blob, err := tc.Save()
+		So(err, ShouldBeNil)
+		So(tc.Dirty(), ShouldBeFalse)
+		another := TagCache{}
+		So(another.Load(blob), ShouldBeNil)
+		So(another.ResolveTag("pkg", "tag:1"), ShouldResemble, common.Pin{
+			PackageName: "pkg",
+			InstanceID:  strings.Repeat("b", 40),
+		})
+	})
+}