How to switch between user roles I have three user roles


Merchant 
Seller
End User


Merchant has more permissions privileges than Seller. Merchant can become a seller or an end user. When i created a user, i assigned all three roles to that user. But when the user is logged in, by default he should only have Merchant privileges. But he can switch to seller or End user from a drop down. The user will not have all permission privileges (Merchant  + Seller + End User) at a time. He will only have a single role at a time. Is there any way to achieve this.
There are couple of module available to do this job. Hope this will be helpful

1. Masquerade


  The Masquerade module allows site administrators (or anyone with
  enough permissions) to switch users and surf the site as that user (no
  password required). That person can switch back to their own user
  account at any time.


2. Role Switcher


  Role Switcher module provides with an option to change role for
  testing purposes. It creates 'roleswitcher' role and grants it
  permission to administer permissions which makes possible to switch
  back to the original role the user had. The module provides a
  roleswitcher block and a page, /roleswitcher.