In https://drupal.org/node/2081207#comment-7909351 it was discovered that adding blocks to the testing profile causes errors, even though they are removed in the setUp().
If blocks are added and then removed again, it should not affect the following tests.
The failing test is testBlockRehash.
It fails on first line:
Drupal\Component\Plugin\Exception\PluginException: The plugin (test_html_id) did not specify an instance class. in Drupal\Component\Plugin\Factory\DefaultFactory::getPluginClass() (line 62 of /var/www/drupal8/core/lib/Drupal/Component/Plugin/Factory/DefaultFactory.php).