I always test the heat of a chili pepper, regardless of if I seed it or not. Because you never know how spicy a chill will be and everyone is different (even when comparing two of the same type), testing the heat of a chili pepper early can save you from fine-tuning later.
To test the chilies heat, slice off the end of one and touch it on your tongue. This will help you gauge how spicy the chili is and how much you should add to your recipe.
I learned this helpful hint from making salsa. Sometimes the salsa is spicy, and sometimes not, regardless if I seed the jalapeño first.