Impossible to enable modules in SimpleTest
You should make triple-sure that your module declares all of its dependencies properly. Even if it does, Simpletest struggles with dependencies and you may have luck if you enable them explicitly in setUp() before your module.

Also, not sure if it's the contributing your error, but instead of $this-&gt;privileged_user = new stdClass(); I would use DrupalWebTestCase::drupalCreateUser like so: $this-&gt;privileged_user = $this-&gt;drupalCreateUser(). I might also declare it after setup() but I'm not sure that's significant.