You can tell if you overmixed your dough by checking for a loose, sticky or wet consistency to the dough.
Or if the dough tears easily and lacks elasticity the dough is overmixed.
For cake batter you can tell if the cake batter is overmixed by checking for a smooth, but dense texture, which means the cake batter is overmixed.
When making cheesecake you don't want any air bubbles in the mixture, which is a result of overmixing.
And if you undermix the cheesecake ingredients it will have lumps and streaks.
You don't want to undermix the ingredients, but you also don't want to overmix the mixture of ingredients either.
If your batter is overmixed, the overmixed batter will look overly uniform and feel dense, heavy or even gloopy.
And after baking, the resulting product will also be dense, rubbery or gummy and may also have a cracked surface or tunneling also known as large holes.
Signs of dough that is over kneaded are a stiff, dense and rubbery texture, a tendency to tear easily when stretched and a lack of elasticity.
Over kneaded dough may also be resistant to reshaping and have a cracked or rough surface.
And the final baked product with overmixed dough will be dry, crumbly and may also have a hard crust.