For buyers contracting authority
Reach for 72254100 when the deliverable is testing a system, not building or running it. A contracting authority uses it for quality assurance, test management, integration and acceptance testing, and the supply of test engineers, often as a standalone activity separate from the development contract.
The boundary worth getting right is against Software development services (72262000). Development produces the software; testing confirms it behaves. Where one contract bundles both, set the primary CPV code by whichever dominates the statement of work, and split into lots if the test workstream is large enough to attract specialist test houses on its own.
Two neighbours sit close. Systems support services (72253200) keeps a live system running rather than verifying a new release, and Systems consultancy services (72246000) advises on system design rather than testing the result. Because 72254100 is the sole child of 72254000, the choice between parent and child is often a formality, so do not over-think it: pick the more specific code and keep the notice description precise about scope.