Testing Rails/Rack applications using rails console - ruby-on-rails-3

Question

My simplistic understanding of the Rails stack is that it does the following (in general)
The input is a HTTP message (GET, POST, PUT, DELETE, HEAD), a URL, some (optional) cookies, a (optional) session token, and possibly some data packed up in JSON or XML format.
This HTTP message is handled by Rack which may run it through a set of "middleware" functions which add or remove data from the message, and may use the data to add, alter, or remove data from the program's data store.
The HTTP message at the output of Rack is sent to the Rails router, which maps it to a controller, an action, and a params hash with the session information, cookies, and other parameters in it. The data is dispatched to the appropriate controller.
The controller method parses the params, and algorithmically combines it with data from the database (via models), optionally changes data and then dispatches a set of variables starting with # to a view template.
The view template takes the data and merges it with the view template to form a view with the appropriate format (eg. HTML, JS, JSON, XML, etc), or it tells the caller (via a HTTP return code) to redirect to another URL.
What I would like to do with my Rails web application, using the Rails console is
Compose a valid HTTP message with URL, session ids, cookies, and encoded data (JSON or XML).
Inject this data into the Rack interface, and inspect what comes out before it is sent to the Rails router.
I would then like to then send that data to the Rails router and see what comes out before it goes to the controller.
I would then like to send that data to the controller and see what comes out before it is sent to the view template.
And I would then like to take that that data and run it through the view template and have display on STDOUT, or have it automatically open a web browser and see it render.
Are there any existing Rails tools which can do this? If not, can anybody point me to the Rails code where these interfaces occur?

Answer 1

Most of what your looking for is within the actionpack library of rails.
ActionDispatch handles the interface with rack, the middleware and the router. The request hits the router as the last piece of middleware. The router itself gets called within action_dispatch/routing/mapper. So if you want to intercept the request before it hits the router, inject your own piece of middleware before the routes get called.
Once the the router map verifies that it has a valid route it calls the application which is over in the railties library. This I believe then bumps you back over into actionpack into the ActionController middleware. I'm not sure exactly where you'd want to tie in to intercept before getting to the controller, but I'm guessing it would be somewhere around that ActionMiddleware class.
From there your off into actionpack. The render/redirect that your controller calls sets up what will happen within actionpack. I'm not sure exactly where AC calls into AP but you should be able to sift your way through it and find the path your looking for.
As for the response, your back to the middleware. Once rails has the view stitched together it basically unwinds itself and goes back down the middleware stack before sending the response back to Rack.
Hope that helps.