def __init__(self, prefix=None, bases=None, args=None):
        assert VALID_FILE_NAME_REGEX.match(prefix), \
            "Virtual test suite prefix '{}' contains invalid characters".format(prefix)
        assert isinstance(bases, list)
        assert args
        assert isinstance(args, list)
        self.full_prefix = 'virtual/' + prefix + '/'
        self.bases = bases
        self.args = args