in general you don't want to add the capacitor. In this case you just need a current limiting resistor, anything bellow 10 and above Vcc/25mA. Just do what Skimask said.

Set pin as output
set it high
Set the pin as input
read it
Set pin as Output
Set it low
Set pin as input
read it

Now compare both reading and have fun with.

It may work in PBP, but i'll suggest some ASM lines.