no spark

hi folks need your input
car ran fine a week ago and now it will not start. found out that there was no spark to the plugs, and no spark coming out of the coil. i have an msd 6al which i tested and it is throwing a good strong spark. i have a mopar performance distributor in it. could it be the coil or distributor? how do you check a coil? can you check the distributor if i'm sending a strong spark from the msd unit? i have checked all grounds and the coil wire.
thanks
terry