How can I programmatically enable clean URLs during a SimpleTest? How can I enable clean URLs from the SimpleTest setUp() method?

Which .htaccess will be used during a simpletest?  I needed to make modifications to RewriteBase to get clean URL's working on the 'non-testing environment', will they carry over to the test environment or do I need to modify .htaccess in setUp() as well?
Did a few tests and here is what I found.

Enable Clean URLs in setUp() method:

function setUp() {
    variable_set('clean_url', 1);
}


.htaccess from live site is used during SimpleTest.  Modifications are not required.