You can proof dry yeast in a small amount of warm water with a little sugar mixed in. And while this is a qualitative way of seeing if your yeast is alive, this method is not reliable to judge if expired yeast is good enough to bake with. You don't know exactly how active or what percentage of yeast is alive or dead using this test. Furthermore, remember that, when yeast die, they may expel compounds that can interfere with the gluten network. This means, if half your packet of yeast is dead, you may run into trouble creating a strong, elastic dough with it.