In a large bowl, combine the beans, cucumber, tomatoes, garlic, onion, parsley, and mint.
For the dressing, in a small bowl, whisk the olive oil and lemon juice until smooth and emulsified.
Pour the dressing over the beans and veggies, add ½ teaspoon salt and black pepper to taste and carefully toss with a large metal spoon. Allow to sit at room temperature for 30 minutes so flavors combine, or refrigerate to serve later.