Hani,
If you are involved in making decisions on a 46" crude oil pipeline YOU SHOULD NOT BE ASKING FOR ADVICE ON AN INTERNET FORUM,
Regards,
Shane

What design code are you using?
What test pressure?, usually 1.1 x DP.

What does it say?

I've never really used API 1110 despite decades in this industry so not sure what it says. But it is an RP, so not as prescriptive as the code.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

well, Wikipedia states that a "hydro test" involves filling the vessel/pipe with a liquid, usually water, so gas is probably not appropriate. https://en.wikipedia.org/wiki/Hydrostatic_test

We've discussed this many times before in the pipeline forum e.g. https://www.eng-tips.com/viewthread.cfm?qid=112658

do a search for "pipeline test in air"

That's a large pipeline and will contain a fair amount of energy which if the pipeline fails could result in a significant crater. you would really need to do your homework on looking at the impact of a failure, whether you can create an exclusion zone ( prob >100m ) / stop vehicles crossing it, that sort of thing.

Many codes and companies and safety authorities won't allow it.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

If safety isn't a concern, go for it....