Is it possible to run functional tests without creating test tables? My goal is to  speed up functional tests without tweaking the database. Is it possible to avoid the creation of Simpletests setup tables and use existing tables instead? I read this article where the author states :

Maybe the answer is Simpletest 2 which allows you to run on a "dirty" environment.


So is this "dirty" environement is the answer? If so, how to use it as setup ?
I have found the answer there. But don't do that ! 

It's better to move the database on a tmpfs folder (it's > 5x faster), because not only a "dirty" environment does not work, but it will broke your website with a serious error (just happened to me).
Hints to tweak the database on this question.

It's there but don't do it :

  // for our functional testing, we want to test the pages and code that
  // we've been generating in the real database. to do this, we need to
  // ignore SimpleTest's normal fake database creation and fake data
  // deletion by overriding it with our own setUp and tearDown. NOTE that
  // if we make our own fake data, we're responsible for cleaning it up!
  function setUp() {
    // support existing database prefixes. if we didn't,
    // the prefix would be set as '', causing failures.
    $this-&gt;setup = TRUE; // Drupal 7 way
  }
  function tearDown() { }