Step 1) Blanch green beans by boiling beans in water for 2 to 3 minutes. Drain; set aside to cool.
Step 2) Place all tomatoes in a large serving bowl.
Step 3) Whisk oil, vinegar, and mustard in a small bowl. Stir in Italian herb seasoning, garlic, salt and pepper. Pour vinaigrette over tomatoes; stir. Add cooled beans; toss gently. Top with feta cheese.