What is the name of a poisonous small shrub with cherry tomato sized berries and dark green leaves?

The poisonous shrub you're describing is likely Solanum dulcamara, commonly known as bittersweet nightshade or climbing nightshade. It produces small, cherry tomato-sized berries that are toxic if ingested. The plant features dark green, lance-shaped leaves and can often be found in damp, disturbed areas. Caution is advised, as the berries can be particularly appealing but are harmful if consumed.