openshift-tests should have tests for egress firewall functionality, including:

• basic functionality in both openshift-sdn and ovn-kubernetes
• port-based rules in ovn-kubernetes
• interaction of NetworkPolicy and egress firewall
• interaction of egress IPs and egress firewall (the latter block the former)
• interaction of egress routers and egress firewall (the former bypass the latter)

https://github.com/openshift/origin/pull/26865