Because finished controls must be built as DLL files in order to be registered as ActiveX/OLE controls, you have two options for testing them as you develop them.
Because you cannot execute a DLL file directly in the Windows environment, the simplest approach is to initially develop the control as an EXE (stand alone executable application), instead of as a DLL. This allows you to execute the control as a stand-alone application and thus build it and execute it as needed to test it out. This method is desirable, but is only appropriate for controls that can behave as standalone applications.
Some controls, however, are not suitable to develop as standalone controls and you will have to write a test application that actually uses your new control to test it appropriately. However, the clock control you will build in this chapter will initially behave in this manner, so you may initially built is as an EXE application. This is because this control will initially simply display a digital clock that ticks each second, and requires no interaction from the application it is being plugged (dropped) into.
For controls that are actually designed to be interactive with another application (controls that are actually driven with method calls from another application they are intended to be dropped into), initial creation as an .EXE application will generally not be appropriate if you wish to test all of the methods out.
Instead, these controls will typically have to be built as true controls (.DLL files), and a separate driver application will have to be developed into which the control will be dropped and executed from to test its behavior.
PowerCOBOL makes handling multiple projects a snap, and this is thus a straightforward process, as will be illustrated later.
