Ability to load fixtures once before test class

Currently we can load fixtures:

• before each test case using PHPUnit setup()
• once before all tests by customizing Symfony bootstrap process like I suggested in liip/LiipFunctionalTestBundle#303

Only the possibility to load fixtures once before test class is missing (like we do with PHPUnit setupBeforeClass()).

So, I would like to add this ability by implementing a simple flag and a $once parameter in methods like loadFixtureFiles() as follows:

public function loadFixtureFiles(array $paths = array(), $append = false, $omName = null, $registryName = 'doctrine', $once = false)

What do you think?

Locate the existing loadFixtureFiles() methods and review how fixtures are loaded during PHPUnit setup. Add coverage for loading fixtures once before a test class, with completion shown by the requested $once behavior and passing tests.