public function testMultipleSetChildrenFail()
 {
     $regexp = new slRegularExpressionSequence($c1 = new slRegularExpressionElement('a'), $c2 = new slRegularExpressionElement('b'));
     try {
         $regexp->setChildren(array(new StdClass()));
         $this->fail('Expected exception.');
     } catch (Exception $e) {
         /* Expected */
     }
 }