Drain and rinse the beans well. Save the remainder for another dish. Peel the tomato (if convenient) by plunging it in boiling water. Cut the tomato into chunks removing the seeds if you prefer. Mix the dressing ingredients (olive oil, balsamic vinegar, garlic, mustard)in a bowl, add the tomato chunks and the beans. Stir in the chopped basil and let the mixture sit for at least an hour to blend the seasonings. This salad can be served stright from the refrigerator but it tastes best freshly made and at room temperature.