Rename deprecated config.serve_static_assets to config.serve_static_files

Author: Ruben Swieringa

test/dummy/config/environments/test.rb

@@ -8,7 +8,7 @@
   config.cache_classes = true
 
   # Configure static asset server for tests with Cache-Control for performance
-  config.serve_static_assets = true
+  config.serve_static_files = true
   config.static_cache_control = "public, max-age=3600"
 
   # Log error messages when you accidentally call methods on nil