Adding a requireToolTip() method for JComponents

public void testTooltip() {
  JComboBox myComboBox = <...>
  assertEquals("Tooltip does not correspond to selection", getToolTipTextInEDT(myComboBox), "expected tooltip");
}

private String getToolTipTextInEDT(final JComboBoxFixture combobox) {
  String tooltip = GuiActionRunner.execute(new GuiQuery<String>() {
    public String executeInEDT() {
      return combobox.component().getToolTipText();
    }
  });
  return tooltip;
}