To make sure your custom form logic in Booker25 is unit tested a global class called Test_FormHelper, is added to the applications. This class contains helper methods that allow you to trigger form events.
Because these methods fire an event as if it was fired from the form to make the behaviour consistent during unit tests and normal operation the default Booker25 handlers are also fired. This means the return value of FormEvent could include FormEvents produced by Booker25.
Using this method, you can trigger a form initialization event to test your custom form implementations.