cache_store has an extra option of :null_store.

guides/source/configuring.textile

@@ -70,7 +70,7 @@ NOTE. The +config.asset_path+ configuration is ignored if the asset pipeline is
 
 * +config.action_view.cache_template_loading+ controls whether or not templates should be reloaded on each request. Defaults to whatever is set for +config.cache_classes+.
 
-* +config.cache_store+ configures which cache store to use for Rails caching. Options include one of the symbols +:memory_store+, +:file_store+, +:mem_cache_store+, or an object that implements the cache API. Defaults to +:file_store+ if the directory +tmp/cache+ exists, and to +:memory_store+ otherwise.
+* +config.cache_store+ configures which cache store to use for Rails caching. Options include one of the symbols +:memory_store+, +:file_store+, +:mem_cache_store+, +:null_store+, or an object that implements the cache API. Defaults to +:file_store+ if the directory +tmp/cache+ exists, and to +:memory_store+ otherwise.
 
 * +config.colorize_logging+ specifies whether or not to use ANSI color codes when logging information. Defaults to true.