Cannellini are white Italian kidney beans. Try substituting cranberry, pinto, or other dried beans in this salad. To save time, canned beans can be used in place of dried.
Prepare an ice bath; set aside. Bring a medium pot of water to a boil over high heat. Add wax beans, and cook until crisp-tender and bright, about 2 1/2 minutes. Remove beans with a slotted spoon, and immediately plunge into ice bath. Drain, and set aside. Repeat with snap peas, blanching them about 1 minute.
Heat the oil in a large saute pan over medium heat. Add scallions and garlic; cook, stirring occasionally, until soft but not browned, about 3 minutes. Add cannellini beans, and cook until just heated through, about 2 minutes more.
Transfer mixture to a large bowl. Add wax beans, snap peas, tomatoes and reserved juice and seeds, and salt. Season with pepper. Using a sharp knife, cut basil into very thin strips; add to bean mixture. Toss to combine; serve warm.