Don't be fooled by cheap USB multimeters

Those things work pretty good, but they are not complete solution. They do work great with fixed loads - something as simple as 5 ohm, 10 watt resistor will work great. I made a little board with 3 resistors and switches for 0.4A, 1A and 2A - but if you don't like soldering, get more resistors and connect them to USB A cables directly.

You'd think you need something smarter than that, but most of the time, the USB power is connected directly to 5V bus, via polyfuse if you are lucky. The amount of motherboards which have (1) per-port current sensor (2) per-port power switch (3) firmware which precisely negotiates current limit is pretty small. Thinkpads seem to be the closest ones, but even they assume 0.5A current limit if nothing is connected to data lines.