Capybara::ElementNotFound: Unable to find field "data" while testing Rails Engines

[onomated]

I'm having problems getting this to work with Rails Engines even after cross referencing several different resources. I'm getting the following error after making calls to set the rack session like so:

page.set_rack_session('warden.user.user.key' => User.serialize_into_session(user).unshift('User'))

Capybara::ElementNotFound: Unable to find field "data"

This is raised on calling fill_in "data", :with => data

I've confirmed that my dummy engine loads and uses the required middleware:

$ rake RAILS_ENV=test middleware
...
use Rack::ConditionalGet
use Rack::ETag
use Warden::Manager
use RackSessionAccess::Middleware
run TestApp::Application.routes

Anything else I may be missing? Here's my spec software stack:

rails (4.2.3)
rspec-rails (3.3.3)
capybara (2.4.4)
rack_session_access (0.1.1)

[ayanko]

What is your actual full spec example?

[onomated]

Just figured out the issue. I was hardcoding the Capybara app to the Rails engine I was testing so it wasn't targeting the dummy app that had the middleware included. Works like a charm now. Thanks a lot for an awesome gem!