If you're using Tsung to test a Rails site that has CSRF protection, Tsung needs to parse the authenticity_token and submit it when POSTing. I could only find outdated examples. The snippet below works.

Tsung Rails authenticity_token

<request>
  <dyn_variable name="authenticity_token" ></dyn_variable> 
  <http url="/registrations/new" version="1.1" method="GET"></http>
</request>

<request subst="true">
  <http url="/registrations" method="POST" version="1.1" 
    contents="authenticity_token=%%_authenticity_token%%&amp;first_name=Jane"/>
</request>

  <request>
    <dyn_variable name="authenticity_token" xpath="/html/head/meta[@name='csrf-token']/@content" />
    <http url="/" version="1.1" method="GET"/>
  </request>

  <request subst="true">
    <http url='/' version='1.1'
       contents='authenticity_token=%%_authenticity_token%%&amp;first_name=Jane'
       content_type='application/x-www-form-urlencoded' method='POST' />
  </request>