The KAIWEETS Electrical Test Kit KIT02 comes with two tools — the KT301T outlet tester and a non-contact voltage pen — packed in foam with a manual and batteries for both, so you are ready to go right from the box. Functioned exactly as described from the first outlet I tried.
The tester plugs into standard three-prong outlet and shows the actual voltage on the LCD screen along with the wiring condition: correct wiring, open ground, open neutral, reversed hot and neutral, and the rest. Holding the button for two seconds trips the GFCI. Auto-hold keeps the result on screen, which matters on outlets you can't see while they're plugged in.
The pen covers what you can't plug into. It switches between a 12V–1000V range and a 70V–1000V range, shows signal strength as a percentage and a bar, has a flashlight in the tip, and beeps faster as you close in on a live conductor.
Worth knowing before you buy: the outlet tester is built for standard 120V three-prong receptacles, so it won't help you with a 240V dryer or range outlet. For everything else in the house, it made testing my sockets a breeze!