I haven't done this, as far as trying out a pattern. But, what I do is, when I buy fabric, I put a picture of the fabric in a file on my computer. Then when I'm ready to start another project, I can look through my fabrics to see what I have on my computer. Or, if I pick out a fabric, but I'm looking to see what I have that will go with it, I look on my computer file first instead of going though my actual fabric.
I don't need to do this often though, as I usually buy by the project and keep those fabrics together. But the file is still a nice reminder of what fabrics I have for that pattern/project in case I decide to change my mind on what to make with that fabric.