in functional test, assert_redirected_to w prefix

I had to use sub-URI deployment (could not use subdomains..), and when
running my functional tests, I the redirected_to assertion embed the
prefix.. quite normal ;-))

is there a way to stipulate this prefix in the test setup to avoid
hard-coding in all the tests ?

Expected response to be a redirect to <>
but was a redirect to <>

/intranet being the prefix in this case ..

many thanks for your suggestions