1. A driver assistance system for a vehicle, said driver assistance system comprising: a camera configured to be disposed at a vehicle equipped with said driver assistance system; wherein said camera, when disposed at the equipped vehicle, views through a windshield of the equipped vehicle; wherein said camera is disposed at a windshield electronics module attached at the windshield of the equipped vehicle; wherein said camera views forwardly through the windshield of the equipped vehicle at a location that is swept by a windshield wiper of the equipped vehicle; said camera capturing image data of a scene forward of the equipped vehicle; a control comprising an image processor; said image processor processing captured image data; wherein said control, responsive to said image processor processing captured image data, detects an object of interest external to the vehicle; wherein said control utilizes a blockage detection algorithm and, responsive to said image processor processing captured image data, is operable to detect at least a partial blocking condition at said camera; and wherein, during end of line vehicle testing of the vehicle at a vehicle assembly plant and with the vehicle driven on rollers to check engine performance, the control does not falsely detect an at least partial blockage condition.