Let's have the following hypothetical case:
- Company develops a product using method 'X' for some testing procedure qualifying it.
- Company releases product, development is frozen, testing no longer takes place, product sells.
- Someone raises an infringement claim over method 'X'.
What this case? The product as-is doesn't incorporate method 'X', it was only used in its development process, so technically the infringement doesn't take place at the time the claim is raised.
What if the product had some qualification based on its development and testing process incorporating method 'X'? Could this revoke that qualification? (maybe this is a bit ridiculous to expect, just for completeness)
Of course it may be possible if necessary to implement a different, non-infringing method for testing then, but this is just the same case like any ordinary patent infringement case.