Testing the spirits deals with all three aspects of discernment: revelation, interpretation and application, although a different kind of spiritual filter needs to be applied to each aspect.
I might pick up a revelation accurately only to interpret it incorrectly. Or I might get a revelation and its interpretation right, only to get stuck on the application (what I am supposed to do with that information?).
For example, let’s say I get a revelation about a political situation, but it happens to touch on a sensitive area in my own experience. If I have hung on to bitterness, for example, my revelation will be tainted by my bitter opinion, which will render my revelation worthless to the kingdom of God.
I need to be mindful of the influences that may come to bear on my thoughts and prayers, and especially on the way I communicate. As I test the spirits around me, I need to include my own spirit, continually consulting with the Holy Spirit for guidance as to what to do.