Interfaces within the IGP—be it ISIS or OSPF—often have rules or conventions regarding their manipulation. Formal out-of-service procedures might require operators to increase metrics before a shutdown or similar. What is unusual and unhelpful is the deletion or removal of an interface from the configuration, especially if it is currently participating in the IGP.
For this test, we make use of jcs:invoke() in order to make an RPC call to query the active interfaces within the protocols. We check the returned list to ensure that each interface is present in the configuration, and for each one that isn't, we emit an error message informing the user of the situation.