Test procedure : We set «1» to PB0 and «0» to PB3. If diode is ok and opens, then at PA0 we have «1». If PA0 is «0», then the the diode has problem. With the program we manage what the PIC will do in each situation . If PA0 is  «1», green led lights wich means that the diode is OK and if PA0 is «0» red led is lighting and the diode is problematic

Test continuous as follows: We give «0» at PB0 and «1» to PB3. If diode is OK and opens, then at PA0 is «1». If PA0 is «0», then diode has problem. If PA0 is «1», green led lights that means that diode is OK and if PA0 is «0» the red diode is lights that means the the diode is problematic.

source code in Assembler