Tests fail because of dependency on messaging

So this line:

$this->drupalGet('admin/messaging/subscriptions/admin');

calls notifications_manage_admin_subscriptions() which calls notifications_subscriptions_operations() which calls:

function _notifications_send_methods($account = NULL) {
  return variable_get('notifications_send_methods', messaging_method_list($account));
}

However messaging module is not installed for this test and so messaging_method_list() is not found and you get a fatal.

Attached patch installs messaging module, which prevents the fatal, however it is possible that instead of adding the dependency we might want to set up a stub function to use for testing purposes and set the notifications_send_methods variable to that as part of test setup.