private static final MutableResource rolesFile = MutableResource.from(Resource.fromString(""));

    @ClassRule
    public static ElasticsearchCluster cluster = ElasticsearchCluster.local()
        .setting("xpack.security.enabled", "true")
        .rolesFile(rolesFile)
        .build();

    public void testUpdateRolesFile() {
        // do stuff

        rolesFile.update(Resource.fromString("""
            user_role:
              cluster: [ALL]
              indices: []
            """));

        // do more stuff
    }