ActionController::MethodNotAllowed
Only get, head, post, put, and delete requests are allowed.

I started getting this funny little error this morning. It is a funny error in the humorous sense, but possibly you need to have used REST to think so. There were a few people getting this problem and finding a few different solutions, but my problem was I had a map.namespace in my routes.rb file. map.namespace appears to be deprecated/abandoned. So I tried using map.resource instead of the map.namespace. Technically I'm looking for a namespace and not a singleton resource, but it worked for me and namespaces and singular resources provide pretty similar functionality in this case. Although I'm still struggling to fix my tests so they they figure out what URL to use.

Update: Singleton resources seemed to cause problems with the :collection option, so now I've rolled my own namespaces with :path_prefix.