title: Ruby, how to create a Rack::Request for testing purposes?
body: <p>I have a library that take a <code>Rack::Request</code> and do stuff on it.</p>
  
  <p>I would like to test it from an <em>unit test</em> and not from a <em>functional test</em>. So I have to create a <code>Rack::Request</code> instance on my own, how can I do it?</p>