bratwurst shelf life
If they pass the smell test and don't have an odd greeny/grey colour, then cook them as you like, but poke an instant-read thermometer in before you eat them . Cook them to 180 degrees Fahrenheit, since it is a ground meat product. Alternately push them out of their casings and use them in a meat loaf, spaghetti sauce, or other long-cooked/boiled recipe.
First: when in doubt, throw it out.
Second: was it this past weekend (I.e.: yesterday) or the weekend before? If it's the latter, I'd be concerned.
Third: are there nitrates or nitrites in the sausage? If so, they're cured or semi-cured and will last much longer than simple "fresh" sausage.