Dressing:
Cook the pasta according to directions (7-12 minutes) until al dente. Siphon off the excess water and allow the pasta to cool. Then pour the pasta into a salad bowl. Wash the tomatoes, remove stalks and cores if necessary, and cut them into slices. Cut the mozzarella into small cubes. Rinse the arugula, spin dry and remove any tough stalks. Cut the arugula into thin strips. Add the tomatoes, mozzarella and arugula to the pasta and mix well.
To make the dressing, mix and whisk the pesto, olive oil, and vinegar. If necessary add a pinch of salt and pepper.
This salad goes well with grilled meat; but it can also be served on its own with a baguette.