You will need to update the phpMyAdmin config file to change the password that is used on starting phpMyAdmin
The exact location of this depends on the testing server package you are using and the OS.
For example, using Mac OS with MAMP as the testing server package:
The MAMP Files are installed to the Applications:MAMP folder
the phpMyAdmin configuration file is located at:
if MAMP is configured to use PHP 5 or
if MAMP is configured for PHP 4
in that file is aline that sets the password using a variable named:
$cfg['Servers'][$i]['password'] = 'test123'; // MySQL password (only needed
// with 'config' auth_type)
edit that line to use the new root password.