more than likely you will test for the company you hire on with.
Every job i ever applied for required a test, some companys may let you roll over certs. but not many.
the only gas line i ever ran was underground and it was 6010++++ bead and hot pass, 7018 fill and cap graded to B31.1
I'm no expert by any means but I'm testing for my high pressure gas and around here it's 6010 all the way out, downhill. That's for the API 1104. Again, not an expert but that's what I've learned. When you say gas though that's what I thought about. Oh yeah, and that is in the 5G, also a test for doing your tie ins on meter sets.