Couscous Chicken Salad

Ingredients:1 1/2 cups fat-free, less-sodium chicken broth12 ounces skinless, boneless chicken breasts1 (10-ounce) package couscous1 cup chopped fresh basil1/4 cup extravirgin olive oil3 tablespoons sherry vinegar3/4 teaspoon salt1/4 teaspoon freshly ground black pepper1 garlic clove, minced1 1/2 cups halved cherry tomatoes1 cup sliced green onions1 (15 1/2-ounce) can chickpeas (garbanzo beans), drained and rinsed