I suggest you install WP in a directory on the client’s web site. It’s easy to do and it will make putting WP into production quite simple.
Briefly, here is what you will be doing:
– download the WP zip file. There is a button at the top of this page to take you to the download page.
– unzip the file into a directory on your computer.
– create a directory for WP under the site’s root directory. I recommend not using the commonly used name wordpress. Make it something, like blogdir, that others are unlikely to guess.
– upload the contents of the directory where you unzipped the zip file to the directory you just created.
Upload the contents of the directory by selecting all of the files and directories and then uploaded. Do not upload just the directory from your computer to the site. If you don’t understand this, let me know.
– you can then run the install steps and can then run WP on the client’s site. As long as you don’t “publish” the URL for WP in a link on another web page are in a forum such as this one, your WP installation should remain invisible to the world.
If you put WP in a directory named blogdir and the client’s site is at http://www.clientsite.com, the URL to get to WP would be http://www.clientsite.com/blogdir/ Give that URL to your client and tell them to keep it secret from those who they don’t want accessing the test site.
– when you want to put WP into production, delete any test posts and comments, and put links to the directory on other pages on the client’s web site, or perhaps into a common menu — you are now in production.
If you want more details about any of these steps, post them in a reply and I’ll answer your questions.
Bob