Add User Testing interface to impl/memory.

service/user/testing.go

Index: service/user/testing.go
diff --git a/service/user/testing.go b/service/user/testing.go
new file mode 100644
index 0000000000000000000000000000000000000000..e9a972b588e77958c979137cfa9d11c996344422
--- /dev/null
+++ b/service/user/testing.go
@@ -0,0 +1,18 @@
+// 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 user
+
+// Testing is the interface that test implimentations will provide.
+type Testing interface {
+	// SetUser sets the user to a pre-populated User object.
+	SetUser(*User)
+
+	// Login will generate and set a new User object with values derived from
+	// email and admin values. It returns the generated clientID.
+	Login(email string, admin bool) (clientID string)
+
+	// Equivalent to SetUser(nil), but a bit more obvious to read in the code :).
+	Logout()
+}