ActionController::TestRequest and query_string

In Rails pre 2.3.x the following could be used in tests:

user_request = ActionController::TestRequest.new(nil,{:application => 'Test'}, nil)
user_request.request_uri = "http://test.com/app/Test/"
user_request.query_string

In the new Rack implementation this should be rewritten a bit

test_request = ActionController::TestRequest.new
test_request.request_uri = "http://test.com/app/test/"
test_request.query_string

But this fails with

NoMethodError: You have a nil object when you didn't expect it!
You might have expected an instance of Array.
The error occurred while evaluating nil.split

This is due to @env['REQUEST_URI'] not being set in query_string in ActionController::Request when using TestRequest.

However the following works:

test_request = ActionController::TestRequest.new
test_request.set_REQUEST_URI('http://test.com/app/Test/')
test_request.query_string

I expected request_uri=() to actually set request_uri but it does not. Using set_REQUEST_URI seems a bit clumsy.