OK; but what (which) test or QA method are we talking about? think

Do you mean this?

What test kit is involved; and who supplies it?

Can (or should) this stuff be done in-house ... or is it only of use when probe repairs have been carried out (eg, by a manufacturer, or third party)?

PS: I'm interested in the scene shown at the banner of your website. Where is that? Not Hexham, surely?

If you don't inspect ... don't expect.