## Software ##
You could use the wiringPi library(you may have to install it) as described in this [question][1].  It tests input, output, pull-up and pull-down. It will return `Failed user gpios: None`if all your pins are OK. 

## Hardware ##
Also, if it returns all clear, make sure that you are observing polarity for LED3. In other words, if you have it in the wrong way it will not work(longer lead is positive). 


  [1]: https://raspberrypi.stackexchange.com/questions/26064/is-my-pis-gpio-damaged