Main Character and friend(s) trying to catch partner cheating

[Kiriko]

Hi, so I’m hoping to get some suggestions of books with the above plot. Please they must be funny or comedic stand-alone books. I’m not picky about Main Character gender but I would prefer heterosexual relationship just because I like the girls vs guys trope. Would love a ‘surprise’ ending which I won’t see coming, with either first person or third person narrative (not a fan of switching POVs). Please no high-school drama, I need a bit of grown-up silliness.
It’s not so much the break-down of the relationship or even the cheating that I’m interested in, rather I want to read about the crazy antics the MC and friends get up to in an attempt to catch the cheating (I wouldn’t mind if there was no cheating at all even)
My apologies if I have a too specific request I just feel like I want to read ‘this’ book (which I have yet to find).
Appreciate all suggestions made as long as it captures the main plot outline I’ll take it.
Thanks

[Rosa]

Out of the Blue?

[MJ]

It's a long shot, but cause you're looking for funny... Janet Evanovich has the Stephanie Plum series. It's up to like 23 books now I think, and there's all sorts of mayhem. Occasionally, some of it is spying on partners/possible partners from memory.

[Kiriko]

Rosa wrote: "Out of the Blue?"
Thanks for the suggestion, I checked it out but I don't think that's what I'm looking for.....