Boil 1 pound mixed green and wax beans in salted water until crisp-tender, 6 minutes; drain. Chop 3 garlic cloves, 2 tablespoons capers and the zest of 1 lemon and mash together to make a coarse paste; saute in olive oil, 2 minutes. Add the juice of the lemon and bring to a boil. Add the beans and toss until glazed, 2 minutes. Season with salt and pepper.