For a while I used successful configuration parsing as the reassuring final step in HubN’s peering tests. It catches syntax errors and unsupported directives, which is useful. It does not tell me what routes a daemon will actually accept, reject or export.
Running the configurations on BIRD, FRR, VyOS and Pathvector found the failures the parser could not: a /128/128 filter, reversed provider and customer labels, ownership checks against the wrong address, and communities which disappeared on the way through.
Those were valid configurations. They just described the wrong network.
The test lab now checks the live RIB and the resulting policy behaviour, including relationship changes and RPKI state transitions. Parsing stays near the start of the test. It no longer gets to call the configuration correct.