Add Consistent(bool) to Testing interface

service/datastore/testable.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 datastore
 
 // TestingSnapshot is an opaque implementation-defined snapshot type.
 type TestingSnapshot interface {
         ImATestingSnapshot()
 }
@@ skipping 23 matching lines @@
         //   SetIndexSnapshot(idxSnap)
         //
         // But depending on the implementation it may implemented with an atomic
         // operation.
         CatchupIndexes()
 
         // SetTransactionRetryCount set how many times RunInTransaction will retry
         // transaction body pretending transaction conflicts happens. 0 (default)
         // means commit succeeds on the first attempt (no retries).
         SetTransactionRetryCount(int)
+
+        // Consistent controls the eventual consistency behavior of the testing
+        // implementation. If it is called with true, then this datastore
+        // implementation will be always-consistent, instead of eventually-consistent.
+        //
+        // By default the datastore is eventually consistent, and you must call
+        // CatchupIndexes or use Take/SetIndexSnapshot to manipulate the index state.
+        Consistent(always bool)
 }