You could add a Working Set that contains only your test project, and use 'Select Working Set...' functionality from the Navigator tab's view menu:
While this won't open the project for you, it WILL make it the only thing you see in navigator or package explorer.
Once you've added it, it will be in a list and you won't need to open the 'Select Working Set...' dialog, just select 'my test project' from the popup menu. It's triggered by that small triangle in the upper right of Navigator, I'm not sure if there is a shortcut.
To switch back to your normal work, simply 'Deselect Working Set' and you will then see everything again.
I also find the 'Collapse All' button/shortcut to be handy when finding things in the Package Explorer or Navigator tabs.