In a small bowl, whisk together vinegar, basil, garlic, and salt. Continue to whisk and add the oil in a steady stream. Set aside.
Bring the water to a boil in a medium saucepan. Add the couscous, cover, and cook on medium-low heat until tender (about 10 minutes). Drain, run under cold water, and let drain again while you make the salad.
In a large bowl, mix together cucumber, tomatoes, onion, beans, and cheese. Add cooled couscous and dressing. Toss and serve immediately or refrigerate.
Like olives? The original recipe called for a couple of ounces of olives. I'm not a huge olive fan, so I left them out. If you add them, the fat, calories, and sodium counts in the recipe will increase.
Vegan? Skip the mozzarella.