The rag doll test shows you more than just viability. Seed sold for planting comes with a seed tag. That tag shows you what percentage germination you should expect based on testing. So, let's says the germination rate is 95% when you buy it. That is close enough to 100% that most folks just ignore it and plant at the recommended rote. Technically to achieve the desired plant density, you should seed at 105% of the rate.
As previously mentioned, store the seed in a cool, dry place where mice and such can't get at it. I typically keep mine in Rubbermaid tubs with lids in the barn.
When you do your rag doll test, if you start with 100 seeds soon before you plant and get 80 to sprout, you simply adjust your planting rate to be 120% of what you would use if planting fresh seed is a near 100% germination rate.
Thanks,
Jack