def get_all_regions(config):
    """Retrieve a set of all regions used by the declared integration tests."""
    regions = set()
    for feature in config.get("test-suites").values():
        for test in feature.values():
            for dimensions_config in test.values():
                for dimensions_group in dimensions_config:
                    regions.update(dimensions_group.get("regions", []))
    return regions