A method for verifying a change to a network , comprising: receiving a network change to be implemented on the network , the network change affecting transfer of data packets through the network ; receiving a network verification test including test parameters , the test parameters including one or more invariants , wherein the one or more invariants include a condition for the transfer of the data packets through the network , and wherein the network verification test tests the transfer of the data packets , and the test parameters identify network elements used by the data packets affected by the network change ; retrieving network data from the network elements identified by the test parameters , wherein retrieving the network data comprises retrieving only network data that is relevant to the test parameters identified in the network verification test ; building a representation of the network from the network data on which to run the network verification test , the representation of the network including representations of the network elements identified by the test parameters , the representation of the network being configured to transfer simulated data packets across the network elements , wherein building the representation of the network includes building the representation of the network only from the network data such that the representation only includes the network elements that are relevant to the network verification test as identified by the test parameters ; and applying the network verification test to the representation of the network data to determine whether the condition included in the one or more invariants is satisfied. receiving a network change to be implemented on the network , the network change affecting transfer of data packets through the network ; receiving a network verification test including test parameters , the test parameters including one or more invariants , wherein the one or more invariants include a condition for the transfer of the data packets through the network , and wherein the network verification test tests the transfer of the data packets , and the test parameters identify network elements used by the data packets affected by the network change ; retrieving network data from the network elements identified by the test parameters , wherein retrieving the network data comprises retrieving only network data that is relevant to the test parameters identified in the network verification test ; building a representation of the network from the network data on which to run the network verification test , the representation of the network including representations of the network elements identified by the test parameters , the representation of the network being configured to transfer simulated data packets across the network elements , wherein building the representation of the network includes building the representation of the network only from the network data such that the representation only includes the network elements that are relevant to the network verification test as identified by the test parameters ; and applying the network verification test to the representation of the network data to determine whether the condition included in the one or more invariants is satisfied. <EOS>