it('should set the model to empty string when empty option is selected', function() {
  scope.robot = 'x';
  compile('<select ng-model="robot">' +
       '<option value="">--select--</option>' +
       '<option value="x">robot x</option>' +
       '<option value="y">robot y</option>' +
      '</select>');
  expect(element).toEqualSelect('', ['x'], 'y');
  browserTrigger(element.find('option').eq(0));
  expect(element).toEqualSelect([''], 'x', 'y');
  expect(scope.robot).toBe('');
});