FWIW, here's my favorite test strip generator. Copy Merge say a 2.5" wide by 14.5" high strip out of your image. File->New. You should see a big white rectangle. Now run the action. Creates 3 layers with Levels adjustments on two of them, with only the middle Levels diamond modified, so it's sort of a gamma bracket. The 3-up test strip will be 3 times wider than your selection. Strip up a bunch of flattened test strips and print them on one large sheet. You can edit the action to change the Levels setting to whatever you want, or even change Levels to Saturation or whatever else you would be pleased to wedge. Wedging is the old word from bracketing. Consult Google for instructions on installing the action.
OK, it's primitive. And it will fail if your selection is too wide. But it's free, and if somebody writes a better action based on this, I expect a copy, OK?