--- a/config/environments/development.rb	Fri May 31 09:45:02 2019 +0900
+++ b/config/environments/development.rb	Sun Jul 14 15:38:04 2019 +0900
@@ -13,36 +13,26 @@
   config.consider_all_requests_local = true
 
   # Enable/disable caching. By default caching is disabled.
-  if Rails.root.join("tmp/caching-dev.txt").exist?
+  # Run rails dev:cache to toggle caching.
+  if Rails.root.join('tmp', 'caching-dev.txt').exist?
     config.action_controller.perform_caching = true
+    config.action_controller.enable_fragment_cache_logging = true
 
-    # config.cache_store = :memory_store
+    config.cache_store = :memory_store
     config.public_file_server.headers = {
-      "Cache-Control" => "public, max-age=172800"
+      'Cache-Control' => "public, max-age=#{2.days.to_i}"
     }
   else
     config.action_controller.perform_caching = false
 
-    # config.cache_store = :null_store
+    config.cache_store = :null_store
   end
 
-  # Don't care if the mailer can't send.
-  # config.action_mailer.raise_delivery_errors = false
-
-  # config.action_mailer.perform_caching = false
-
   # Print deprecation notices to the Rails logger.
   config.active_support.deprecation = :log
 
-  # Raise an error on page load if there are pending migrations.
-  # config.active_record.migration_error = :page_load
 
-  # Debug mode disables concatenation and preprocessing of assets.
-  # This option may cause significant delays in view rendering with a large
-  # number of complex assets.
-  # config.assets.debug = true
-
-  # Raises error for missing translations
+  # Raises error for missing translations.
   # config.action_view.raise_on_missing_translations = true
 
   # Use an evented file watcher to asynchronously detect changes in source code,