module ActionDispatch::TestProcess

def assigns(key = nil) 

def assigns(key = nil)
  assigns = {}.with_indifferent_access
  @controller.instance_variable_names.each do |ivar|
    next if ActionController::Base.protected_instance_variables.include?(ivar)
    assigns[ivar[1..-1]] = @controller.instance_variable_get(ivar)
  end
  key.nil? ? assigns : assigns[key]
end

def cookies 

def cookies
  @request.cookies.merge(@response.cookies)
end

def fixture_file_upload(path, mime_type = nil, binary = false)

post :change_avatar, :avatar => fixture_file_upload('/files/spongebob.png', 'image/png', :binary)

This will not affect other platforms:
To upload binary files on Windows, pass :binary as the last parameter.

post :change_avatar, :avatar => fixture_file_upload('/files/spongebob.png', 'image/png')

Shortcut for ARack::Test::UploadedFile.new(ActionController::TestCase.fixture_path + path, type): 
def fixture_file_upload(path, mime_type = nil, binary = false)
  fixture_path = ActionController::TestCase.send(:fixture_path) if ActionController::TestCase.respond_to?(:fixture_path)
  Rack::Test::UploadedFile.new("#{fixture_path}#{path}", mime_type, binary)
end

def flash 

def flash
  @request.flash
end

def redirect_to_url 

def redirect_to_url
  @response.redirect_url
end

def session 

def session
  @request.session
end