The Delphi unit that you develop for extensibility must include the following items:
One or more Agent Objects; one Agent Object for each type of control that you want to support. The Agent Objects interface between UFT One and the Delphi controls in the application being tested.
One factory function that creates the appropriate Agent Object for each control. When UFT One first interacts with a control, it calls the factory function to create the corresponding Agent Object.
For some custom controls, mapping the control to an existing Delphi test object class might provide sufficient support. In such cases, you do not have to design an Agent Object for the control.