LRT numerous fics who try to do this also do this terribly, for various reasons

- safe sex convo in the middle of a sexual encounter, rather than in a context where sex isn't expected to directly follow

- safe sex convo where characters talk and decide not to use protection (call me jaded but I almost never see a fic where I would make the same decision that these characters made in that scenario, it just feels like lip service)

- assuming safe sex practices only apply to PIV sex. if you mention testing, you acknowledge that STIs exist in the world you created, and STIs are also transmitted by oral and digital sex. I don't know if in my decade of reading smut I've seen protection used for oral

You don't have to encorporate safe sex in your fic to send a message. if it's what you want to write, please write it! but if its for an educative purpose, you can just leave that to the professionals