How do you know when a sweet potato pie is done?

When a baked potato is cooked it should be crisp outside and soft inside. Not all methods of baking produce a crisp finish, and potatoes baked in their jackets aren't usually crisp because the skins don't crisp as effectively as the outside of peeled potatoes.

To check whether a potato is done inside you could insert a thin sharp object such as a fine skewer or narrow unserrated knife. Move the knife or skewer slightly inside the potato to test for give, that is, movement inside.

If the potato isn't cooked through there will be inner resistance rather than a soft texture.

Or you can simply cut the potato in half and check the centre. If it isn't done, you simply continue cooking the two halves; this will make no difference to the finished food unless you particularly need the potatoes to be cooked whole.