Add an option in phpunit config to clear the cache before tests are run

[adrienbrault]

Hello,

This fixes #374

[fabpot]

I don't like adding more options. It should be better to add a note in the documentation about that. Should be more than enough, especially because the files that are changed are part of the user project and not Symfony.

[ericclemmons]

What's the reason for blowing the cache before running the tests? Is it because you have custom files (like configs, templates, etc.) that aren't being recompiled in the container?

If so, perhaps the solution is a cookbook article on adding custom FileResources to the container so that they're automatically checked for changes when the tests are ran.

(I had the same problem & solved it that way)