In a large saucepan of lightly salted boiling water, cook the green beans uncovered for 7 to 9 minutes or until tender. Drain and rinse in cold water. In a small bowl, whisk together the olive oil, vinegar, mustard, and salt. Pour the dressing over the green beans and toss well. Fold in the tomatoes and goat cheese, then add pepper to taste.
To make up to 2 days ahead, prepare and store separately in the refrigerator: green beans, dressing, tomatoes, and cheese. Combine up to 3 hours before serving.