Basic pluto with IKEv2 on the initiator (west), and on the responder.

However, this test checks to see if the responder accepts a more
narrowed down proposal as per https://tools.ietf.org/html/rfc5996#section-2.9

The initiator asks for all protocols and ports. The responder only allows
tcp and port 1234

Because narrowing=yes on the responder, it will allow and suggest its
narrowed proposal. Because the initiator has narrowing=yes, it should
accept the narrowed proposal and install it.