Simulate soundcard in order to test audio program

I am currently developping an audio application using Portaudio.
In order to test it, I would like to be able to control the input and thus check the output of my application. However, I would love to achieve this only internally.

Do you know some software able to emulate a soundcard, whose output would be the input of my Portaudio program and whose input would be the output of my Portaudio program ?

Thank you in advance,
Jean.