Database Test Case Must Purge Extension Schema When Done

The schema.json files created for extensions by the database test case need to be erased/purged after tests are run. If not, then they become stale on locally run tests, which can lead to false test failures during extension development.

I think this just needs an

unlink(self::$schema_file);

in the tearDownAfterClass method, like:

	static public function tearDownAfterClass()

	{

		if (self::$schema_file !== '')

		{

			copy(self::$phpbb_schema_copy, self::$install_schema_file);

			unlink(self::$schema_file);

		}

		parent::tearDownAfterClass();

	}

Otherwise, perhaps storing these files in the phpBB/cache will work too, as that is a regularly purged.