The feeders of a continuous proportioning systems are normally installed to discharge into a collecting conveyor. In making this installation, provision must be made for these feeders to be tested. This provision for testing may be done by inserting a valve on the feeder discharge --- one way from the valve, the feeder flow would go to a test spout; the other way, it would go to the collecting conveyor. Or, if it is a volumetric screw feeder that is being used, a slide gate may be installed in the trough before the feeder discharge, so it can be used for testing. Regardless, a means of testing must be provided for in continuous proportioning systems.