There is nothing worse than making a batch of bread only to find that the yeast was stale and the bread didn't rise. To test that your yeast is still active, sprinkle the instant yeast granules onto 2 tablespoons of water in a small bowl. Leave to stand for 5 minutes. If the yeast forms bubbles it is still fresh and you can use that yeast mixture in your recipe. If it doesn't foam, it means the yeast is dead and you need to buy fresh.