Integration::Session fails to follow_redirect! because of Rack headers['location] changes

Given a freshly created edge app and a controller (e.g. Posts) that just redirects one URL to another URL (e.g. /posts/private =302=> /posts/index ) the following simple steps in an Integration story fail.

get '/posts/private' 
assert_response :redirect # passes
follow_redirect! # should try to get /posts/index
assert_response :success # fails with a 404

What happens is that no matter what the URL follow_redirect! always tries to get /h which is actually the wrongly interpreted first character of http://www.example.com/posts/index

I've tracked the issue down to line 129 of integration.rb:

get(interpret_uri(headers['location'].first))

The bug seems to have appeared after this commit:

http://github.com/rails/rails/co...

Before these Rack related changes, calling headers['location'] would return an Array of Strings. Now it returns a single String (in my case http://www.example.com/posts/index) and calling first on it returns the first character.

Removing the call to first makes my integration story pass but raises an error in line 35 of integration_test.rb (test_follow_redirect_calls_get_and_returns_status):

@session.stubs(:headers).returns({"location" => ["www.google.com"]})

The test can be fixed by removing the square brackets i.e. make headers['location'] stub return an String.

I am almost certain that the test needs fixing because line 342 of Rack's lint.rb (Rake::Lint#check_headers) that states that "header values must consist of Strings" and it seems to be exactly what is returned from the @app.call(env)

http://github.com/chneukirchen/r...

I am attaching a tiny patch for this with no extra tests, just the corrected ones, as the dispatch code is way over my head and I can't seem to find a way to test it more end to end. Testing with stubs seems to have hidden the bug in this case...