Auto detect LED failure
Component Failures fall in to 3 categories and generally in this order;


Bad Process ( solder, handling and ESD control )
Bad Design  
Bad Part


Considering LED's are all factory tested 100% for Iv (Luminous Intensity), I suggest you illuminate us with pertinent details that might explain 1. or 2. 
Then you wont have an issue with 3.

ESD damage can cause early failure or immediate failure unless you choose parts with Diode protection built in or use them in back-to-back mode parallel mode where bi-colour depends on polarity and interpolated color depends on duty cycle.

Why waste time testing LEDs that were already good and spend time instead looking for anything that can cause >-5V > 100uA. You are probably contributing to the failures without knowing it.