Just had a look at my Utilities folder...
It's awfully empty. Seems I haven't done anything with Wifi since the last clean install...
I use Wireless diagnostics mostly, available by ALT-clicking the Wifi icon in the menu bar. That gives enough overview in most cases.
If you need more, Netspot will put your routers on a map. Nice to work out how many routers you need to put in and where they should go.
I used to use AirMagnet too, but it seem to have been scooped up by the corporate world (Netscout) and they are set to confuse us, by offering at least a dozen different utils for what one app used to do.
Quite honestly, I don't remember the Mac tools for Wifi. They seem to have gone very commercial or turned into adware. Must be the appstore's influence. Tried a few minutes to find a few names on the appstore, but this didn't even turn up one suggestion. Loads of VPN and photo sync crap, tho...
These days, my colleague who is doing large scale Wifi deployment, uses a cheap router with some open source distro on it to analyse. That thing is put in the location studied and remains there for a few weeks. Data is analysed afterwards.