Peter over at Electronics-Lab posted an article describing how he designed and built his simple SMD LED tester:
This project is a simple LED tester and LED polarity checker. It can be used to check 1206, 0805, 0603 and 5mm LEDs. All parts are readily available and they are very cheap. Usage is very simple. Just press the tack switch to first check the battery is good. The blue led will turn on. Now you are ready to test your leds and check their polarity.