UPDATE 23 Dec
I had the problem where Zend Framework complains about "No default module defined for this application". I didn't use Modules and the main app works fine. 
I finally solved the problem with the help from weierophinney.net
  Your bootstrap needs to minimally set the controller directory -- do a call to $this->frontController->addControllerDirectory(...) in your appBootstrap() method. I didn't in my example, as my Initialization plugin does that sort of thing for me.
The problem is solved by adding the below to setUp()
$this->getFrontController()->setControllerDirectory(APPLICATION_PATH . '/controllers');
But now, I have afew other questions: 
1. Why does that value not get initialized by application.ini?
In application.ini, I have 
[production]
resources.frontController.controllerDirectory = APPLICATION_PATH "/controllers"
[testing : production]
// didn't change anything regarding modules nor controllers
2. I tried setting the controllerDirectory in bootstrap.php of my unit test, but it does not work
$front = Zend_Controller_Front::getInstance();
$front->setControllerDirectory(APPLICATION_PATH . '/controllers');
The only way that works is using setUp(). Why is that?
END UPDATE 23 Dec
I am getting the above error when unit testing my controller plugins. I am not using any modules. in my bootstrap.php for unit testing, I even tried adding
$front = Zend_Controller_Front::getInstance();
$front->setDefaultModule('default');
But it still does not work. Anyways my bootstrap.php looks like this
UPDATE: the error looks something like
There were 2 errors:
1) Application_Controller_Plugin_AclTest::testAccessToUnauthorizedPageRedirectsToLogin
Zend_Controller_Exception: No default module defined for this application
D:\ResourceLibrary\Frameworks\PHPFrameworks\Zend\Controller\Dispatcher\Standard.php:391
D:\ResourceLibrary\Frameworks\PHPFrameworks\Zend\Controller\Dispatcher\Standard.php:204
D:\ResourceLibrary\Frameworks\PHPFrameworks\Zend\Controller\Dispatcher\Standard.php:244
D:\ResourceLibrary\Frameworks\PHPFrameworks\Zend\Controller\Front.php:954
D:\ResourceLibrary\Frameworks\PHPFrameworks\Zend\Test\PHPUnit\ControllerTestCase.php:205
D:\Projects\Tickle\tests\application\controllers\plugins\aclTest.php:6
2) Application_Controller_Plugin_AclTest::testAccessToAllowedPageWorks
Zend_Controller_Exception: No default module defined for this application
D:\ResourceLibrary\Frameworks\PHPFrameworks\Zend\Controller\Dispatcher\Standard.php:391
D:\ResourceLibrary\Frameworks\PHPFrameworks\Zend\Controller\Dispatcher\Standard.php:204
D:\ResourceLibrary\Frameworks\PHPFrameworks\Zend\Controller\Dispatcher\Standard.php:244
D:\ResourceLibrary\Frameworks\PHPFrameworks\Zend\Controller\Front.php:954
D:\ResourceLibrary\Frameworks\PHPFrameworks\Zend\Test\PHPUnit\ControllerTestCase.php:205
D:\Projects\Tickle\tests\application\controllers\plugins\aclTest.php:16
UPDATE
I tried adding 
public function setUp() {
  $front = Zend_Controller_Front::getInstance();
  $front->setDefaultModule('default');
}
then 1 part works. 
public function testAccessToUnauthorizedPageRedirectsToLogin() { // this fails with exception "Zend_Controller_Exception: No default module defined for this application"
  $this->dispatch('/projects');
  $this->assertController('auth');
  $this->assertAction('login');
}
public function testAccessToAllowedPageWorks() { // this passes
  $auth = Zend_Auth::getInstance();
  $authAdapter = new Application_Auth_Adapter('jiewmeng', 'password');
  $auth->authenticate($authAdapter);
  $this->dispatch('/projects');
  $this->assertController('projects');
  $this->assertAction('index');
}