Pasta Salad

Ingredients

• 1 1/4 c. mayonnaise
• 2 Tbsp. prepared mustard
• 1 tsp. dried tarragon
• 1/2 tsp. salt
• 1/8 tsp. pepper
• 2 c. seashell pasta, cooked and drained
• 1 (9 oz.) pkg. frozen cut green beans, cooked and drained
• 1 (6 1/2 oz.) can tuna, drained and flaked
• 1/4 c. coarsely chopped red onion