A contrived example of a problem I'm have testing sessions in Sinatra with Rack::Test

hello.rb

require 'sinatra/base'

class HelloApp < Sinatra::Base
  enable :sessions

  get '/' do
    "Hello, #{session[:user]}" 
  end

  post '/' do
    session[:user] = params[:user]
    redirect '/'
  end
end

require 'test/unit'
require 'rack/test'

class HelloTest < Test::Unit::TestCase
  include Rack::Test::Methods

  def app
    HelloApp
  end

  def session
    last_request.env['rack.session']
  end

  def test_post_demonstrating_sessions_work
    post '/', { :user => "Jason" }
    follow_redirect!
    assert_equal "Hello, Jason", last_response.body
  end

  ###
  # These two tests below fail:
  ###

  # Trying this the only way I've seen given as an example:
  def test_get_setting_session_from_request
    get '/', {}, { 'rack.session' => { :user => "Jason" } }
    assert_equal "Hello, Jason", last_response.body, "'Jason' was never put in session[:user]"
  end

  # /shrug
  def test_get_setting_session_from_request_another_way
    get '/', {}, { :session => { :user => "Jason" } }
    assert_equal "Hello, Jason", last_response.body, "'Jason' was never put in session[:user]"
  end

end

hello_2.rb

require 'sinatra/base'

class HelloApp < Sinatra::Base
  enable :sessions

  get '/' do
    "Hello, #{session[:user]}" 
  end

  post '/' do
    session[:user] = params[:user]
    redirect '/'
  end
end

require 'test/unit'
require 'rack/test'

class HelloTest < Test::Unit::TestCase

  def setup
    @browser = Rack::Test::Session.new(Rack::MockSession.new(HelloApp))
  end

  def session
    last_request.env['rack.session']
  end

  def do_login!
    @browser.post '/', { :user => "Jason" }
  end

  def test_post
    do_login!
    @browser.follow_redirect!
    assert_equal "Hello, Jason", @browser.last_response.body
  end

  def test_get
    do_login!
    @browser.get '/'
    assert_equal "Hello, Jason", @browser.last_response.body, "'Jason' was never put in session[:user]"
  end

end