message: better header
diff: .test-selector .header {
  display: flex;
  + align-items: center;
  + padding: 5px 0;
  +}
  +
  +.test-selector .header h2 {
  + flex-grow: 1;
  +}
  +
  +.test-selector .header button {
  + margin: 0;
  + padding: 0;
  }
  