Well, no pics for this, but I always test a fabric before putting it away in my stash. Here is what I do.
Just cut a small snip off one of the corners of several fabrics and place them in a bowl of very hot water. Let them sit for a little while. Then take them out and sandwich them between either two pieces or a strip folded over of white muslin. Make sure the muslin is also wet. Let it all stay like that until the muslin is dry. Unfold and see if there are any spots of color. If so, wash the fabric and then retest. If it continues to bleed, it is out of there.