Temporary login for test users

Hello,

I want to ask you some questions about some issues I have,
but therefor i need you to view the site i’m working on.

But i’m using the ‘Under Construction’ plugin, because the site’s not ready yet.

How can I let you view my site, without my client , or anybody else, seeing it yet.

I was thinking about a temporary login or something like that.

Thanks in advance!