How To Test a New User Account and Password? - MySQL FAQs - Managing User Accounts and Access Privileges

If you have new user created with a password, you test it using "mysql" program with the "-u" and "-p" options. The following tutorial exercise shows you some interesting use cases of connecting to the server with user names and passwords:

>cd \mysql\bin
>mysql -u dev
ERROR 1045 (28000): Access denied for user 'dev'@'localhost'
 (using password: NO)

>mysql -u dev -pTEST
ERROR 1045 (28000): Access denied for user 'dev'@'localhost'
 (using password: YES)

>mysql -u dev -pretneciyf
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 39 to server version: 5.0.24-community

Type 'help;' or '\h' for help. Type '\c' to clear the buffer.

mysql> use test;
Database changed

mysql> SHOW TABLES;
+----------------+
| Tables_in_test |
+----------------+
| articles       |
| links          |
+----------------+
2 rows in set (0.04 sec)