I always revise but as soon as I sit a test the material that I revised goes out

The problem seems to be the confidence. What you should do is, revise several times. Every time you revise try not to look at the notes as much as you did the last time. And keep in mind that while revising keep your speed faster then normal reading. Reading fast would strengthen your previous established links in the brain instead of creating a new link for the same learning point. All the best. Cheers, {:-))