Wrong Cliffie.   Test pressings were done on the regular vinyl used for production.  The original reason was to send copies to the label and/or producer to compare the quality of the metalwork and see if this was a good representation of the approved mastering.  Historically 3 or 4 copies were supplied but as the years progressed more were pressed to provide advance copies to the most important media folks. 
 
Devoting a single press to "lesser quality" vinyl for tests would be economically silly for the plant.