How do you know if eggplant is still good?

To determine if an eggplant is still good, check for firmness; it should feel solid and not soft or mushy. Look for smooth, shiny skin without any dark spots, wrinkles, or blemishes. Additionally, gently press the skin; it should spring back, indicating freshness. If the eggplant has a sour smell or shows signs of mold, it's best to discard it.