Building a tester for 5VDC 2A power adapters
Here's a basic tester:







simulate this circuit &ndash; Schematic created using CircuitLab

D1 should be something in the visible spectrum.

If you need to know the exact voltage then get a voltmeter module from e.g. eBay. If you need to know if it can output all 2A then you'll need to get a dummy load.