public function testToString()
 {
     $p = new Zend_Exception('p', 0);
     $e = new Zend_Exception('e', 0, $p);
     $s = $e->__toString();
     $this->assertContains('p', $s);
     $this->assertContains('Next', $s);
     $this->assertContains('e', $s);
 }