Implement a server-side config service interface.

server/config/format_test.go

Index: server/config/format_test.go
diff --git a/server/config/format_test.go b/server/config/format_test.go
new file mode 100644
index 0000000000000000000000000000000000000000..7b95316c48578a12195bc5da3563ef59da61578d
--- /dev/null
+++ b/server/config/format_test.go
@@ -0,0 +1,112 @@
+// Copyright 2016 The LUCI Authors. All rights reserved.
+// Use of this source code is governed under the Apache License, Version 2.0
+// that can be found in the LICENSE file.
+
+package config
+
+import (
+	"testing"
+
+	"golang.org/x/net/context"
+
+	. "github.com/smartystreets/goconvey/convey"
+)
+
+// retainingBackend is a simple Backend implementation that retains the last set
+// of data that it received.
+type retainingBackend struct {
+	Backend
+
+	lastItems []*Item
+	lastErr   error
+}
+
+func (b *retainingBackend) Get(c context.Context, configSet, path string, p Params) (*Item, error) {
+	var item *Item
+	item, b.lastErr = b.Backend.Get(c, configSet, path, p)
+	b.lastItems = []*Item{item}
+	return item, b.lastErr
+}
+
+// GetAll implements Backend.
+func (b *retainingBackend) GetAll(c context.Context, t GetAllType, path string, p Params) ([]*Item, error) {
+	b.lastItems, b.lastErr = b.Backend.GetAll(c, t, path, p)
+	return b.lastItems, b.lastErr
+}
+
+type customFormatter string
+
+func (cf customFormatter) FormatItem(c string, fd string) (string, error) {
+	return string(cf), nil
+}
+
+type retainingResolver struct {
+	format string
+	item   *Item
+}
+
+func (rr *retainingResolver) Format() (string, string) { return rr.format, "" }
+func (rr *retainingResolver) Resolve(it *Item) error {
+	rr.item = it
+	return nil
+}
+
+type panicFormatter struct{}
+
+func (pf panicFormatter) FormatItem(string, string) (string, error) { panic("panic") }
+
+func TestFormatBackend(t *testing.T) {
+	t.Parallel()
+
+	Convey(`A testing environment`, t, func() {
+		tb := testingBackend{
+			items: []*Item{
+				{Meta: Meta{"projects/foo", "path", "####", "v1"}, Content: "foo"},
+				{Meta: Meta{"projects/bar", "path", "####", "v1"}, Content: "bar"},
+			},
+		}
+
+		// Pass all things from the backend through the formatter.
+		var fr FormatterRegistry
+		fb := FormatBackend{
+			Backend:     &tb,
+			GetRegistry: func(context.Context) *FormatterRegistry { return &fr },
+		}
+
+		// Retain all raw Items that were returned for examination.
+		rb := retainingBackend{
+			Backend: &fb,
+		}
+
+		c := context.Background()
+		c = WithBackend(c, &rb)
+
+		Convey(`Will panic if an attempt to register empty key is made.`, func() {
+			So(func() { fr.Register("", nil) }, ShouldPanic)
+		})
+
+		Convey(`Will ignore items that have already been formatted.`, func() {
+			rr := retainingResolver{"test", nil}
+			fr.Register("test", panicFormatter{})
+
+			// Confirm that this setup correctly attempts to format the item.
+			So(func() { Get(c, AsService, "", "", &rr, nil) }, ShouldPanic)
+
+			// Now, pretend the item is already formatter. We should not get a panic.
+			tb.items[0].Format = "something"
+			So(Get(c, AsService, "", "", &rr, nil), ShouldBeNil)
+		})
+
+		Convey(`Testing custom formatter`, func() {
+			cf := customFormatter("content")
+			fr.Register("test", cf)
+
+			// Confirm that this setup correctly attempts to format the item.
+			rr := retainingResolver{"test", nil}
+			So(Get(c, AsService, "", "", &rr, nil), ShouldBeNil)
+			So(rr.item, ShouldNotBeNil)
+			So(rr.item.Format, ShouldEqual, "test")
+			So(rr.item.Content, ShouldEqual, "content")
+		})
+	})
+}