What dark green heart shape vine grows a long green fruit?

The plant you're describing is likely the "heart-shaped" or "string bean" variety of the Mung Bean (Vigna radiata) vine. This vine features dark green, heart-shaped leaves and produces long, thin green pods that contain edible beans. Another possibility is the Snake Gourd (Trichosanthes cucumerina), which also has heart-shaped leaves and produces long, slender fruits. Both plants are known for their distinctive foliage and elongated fruit.