Trying to figure out if your dry yeast is still good for baking? It's really simple to learn how to test yeast for viability in about 10 minutes.
Measure out 2¼ teaspoons of dry yeast (active, quick rise, etc.) into a small bowl. Add 1 teaspoon of granulated sugar, and combine the two ingredients.
Now you will need to add warm water to the yeast and sugar, BUT there is a catch! The water needs to be at 110°F. to activate the yeast. If the water is too hot, it will kill the yeast. The way I do it is to bring some water to almost a boil, then pour out ¼ cup of it into a measuring cup. Let let the water slowly drop in temperature until it registers 110°F. on a digital thermometer. As soon as it hits 110 degrees, pour the water into the yeast mixture and stir well, to combine. Once combined, set the bowl aside for 10 minutes.
After 10 minutes, check on yeast. You should have a bubbly mixture that smells very "yeasty". If bubbles are non-existent, the yeast is unfortunately dead as a doorknob. IF the yeast is bubbly and has a yeasty aroma, then it can still be used for recipes that call for yeast. Discard your yeast experiment, and use unused yeast to bake away!
How To Test Yeast For Viability https://www.thegratefulgirlcooks.com/how-to-test-yeast-for-viability/