Testing with air pressure always scares me! Air is compressible and like any spring has the capability to explode violently and with a lot of energy. Have you considered converting your set up to water? Water is an incompressible fluid and for pressure testing is way safer! One can find small, high pressure, hand operated pumps online that you can hook up to a standard garden hose click here . I have not used this brand before but you can find other hand pumps I'm sure that are cheaper and will perform the same task!
With a water pressure testing system if your Wilkerson ever malfunctioned catastrophically it would be a lot safer and less violent. Having said this, your safest choice-even with water, when it comes to pressure testing is Distance! The "BANG" from imploding volumes always makes me jump-even when I know it is approaching its crush depth!