Zend_Mail::clearDefaultFrom PHP Method

    public static function clearDefaultFrom()
    {
        self::$_defaultFrom = null;
    }

 public function testDefaultFrom()
 {
     Zend_Mail::setDefaultFrom('*****@*****.**', 'John Doe');
     $this->assertEquals(array('email' => '*****@*****.**', 'name' => 'John Doe'), Zend_Mail::getDefaultFrom());
     Zend_Mail::clearDefaultFrom();
     $this->assertEquals(null, Zend_Mail::getDefaultFrom());
     Zend_Mail::setDefaultFrom('*****@*****.**');
     $this->assertEquals(array('email' => '*****@*****.**', 'name' => null), Zend_Mail::getDefaultFrom());
 }