I have installed Mobile Joomla! on a localhost site, but when viewed in Chrome Tools mobile emulation mode, I see no difference at all, including not seeing an advertisement, as was noted in the documentation.  So I believe I am not seeing Mobile Joomla! at all.  How can I verify Mobile Joomla! is working?

MobileJoomla detects kind of device (desktop/smartphone/tablet) at first visit and stores it in cookie (for performance reason). Just open Chrome Emulator in Incognito mode, choose device to emulate, and then only visit website to test.

Alternatively, it's possible to force device modes by using device= parameter:
website.com/?device=xhtml - Smartphone mode
website.com/?device=iphone - iPhone mode
website.com/?device=desktop - Desktop mode