Make obtaining the Testable interface actually part of the interface.

impl/dummy/dummy.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 dummy
 
 import (
         "fmt"
         "runtime"
         "strings"
@@ skipping 99 matching lines @@
 func Memcache() memcache.RawInterface { return dummyMCInst }
 
 /////////////////////////////////// tq ////////////////////////////////////
 
 type tq struct{}
 
 func (tq) AddMulti([]*taskqueue.Task, string, taskqueue.RawTaskCB) error { panic(ni()) }
 func (tq) DeleteMulti([]*taskqueue.Task, string, taskqueue.RawCB) error  { panic(ni()) }
 func (tq) Purge(string) error                                            { panic(ni()) }
 func (tq) Stats([]string, taskqueue.RawStatsCB) error                    { panic(ni()) }
+func (tq) Testable() taskqueue.Testable                                  { panic(ni()) }
 
 var dummyTQInst = tq{}
 
 // TaskQueue returns a dummy taskqueue.RawInterface implementation suitable for
 // embedding.  Every method panics with a message containing the name of the
 // method which was unimplemented.
 func TaskQueue() taskqueue.RawInterface { return dummyTQInst }
 
 /////////////////////////////////// i ////////////////////////////////////
 
@@ skipping 18 matching lines @@
 func (i) IsCapabilityDisabled(err error) bool                                      { panic(ni()) }
 func (i) IsOverQuota(err error) bool                                               { panic(ni()) }
 func (i) IsTimeoutError(err error) bool                                            { panic(ni()) }
 
 var dummyInfoInst = i{}
 
 // Info returns a dummy info.Interface implementation suitable for embedding.
 // Every method panics with a message containing the name of the method which
 // was unimplemented.
 func Info() info.Interface { return dummyInfoInst }