A method includes receiving, by a computing system, a declarative testing descriptor for active testing of a network slice implemented by first virtualized services in a network; receiving, by the computing system and from an orchestration layer, metadata associated with the network slice; determining, by the computing system and based on the declarative testing description and the metadata, active testing configuration for testing the network slice; and starting an active test according to the active testing configuration and determining service level violations based on a result of the active test.