When I launch 10 consecutive tests on a web site that needs basic authentication, the first connection always takes much more time.
Are the credentials store after the first connection ? How could I avoid this storage to test a real first connection each time ?
The credentials are not stored on the browser side. What you are probably seeing is server-side caching. On the first request the credentials have not been accessed in quite a while and the server probably needs to go to disk (or some external system). On subsequent visits the server already has the credentials in RAM (even if it is just the OS filesystem cache) so it is a lot faster.