I'm using rails (3.0.4) and rspec-rails (2.5.0). When I run rails generate rspec:install it produces spec_helper.rb that contains this line:
rails generate rspec:install
ENV["RAILS_ENV"] ||= 'test'
When I run rake spec I get this warning on in the terminal:
DEPRECATION WARNING: RAILS_ENV is deprecated. Please use ::Rails.env.
One would be tempted to simply replace the ENV in spec_helper.rb with ::Rails.env but (e.g. solution on Stack Overflow ) but Rails.env returns "development" at that point so the line has no effect and leaves tests running in the development environment.
That warning is telling you that the constant RAILS_ENV is deprecated, not the the environment variable ENV["RAILS_ENV"]. If you clone the Rails repo and check out the v3.0.4 tag, and search for RAILS_ENV, you'll see that Rails, itself, uses ENV["RAILS_ENV"] in several places.
Must be coming from somewhere else in your app.