To reduce the number of visitors to your test site, I would also add entries to robots.txt, requesting that search engines not index the folder where you run the test site.
I echo the earlier warnings about running a test site off the Production database. Stuff happens -- the easiest mistake to make would be to get the database table prefix in the test system set to the Production tables. Then again, you could almost as easily get the database name wrong in your test system, and have it muck up the Production database. Which makes a good argument for having different database ID and password for the test database. The ideal approach is to run the test system "somewhere" where it can be stopped from accessing the Production database. Personally, I have not gone that far under the assumption that I couldn't afford the solution, but I haven't looked carefully enough to know for sure.
One final word of warning, and perhaps the most important, about development/test WordPress installations: if you are doing much php or MySQL query work, runaway "tasks" can get you thrown off your web hosting account "for life". That will have a huge impact on your Production web site. Only solution that I know of is a local test environment on your own hardware (e.g. - LAMP on your workstation) to do initial debugging of php and MySQL queries, before moving testing to your web host-based test environment.