@Override
    public List<OsmRelationInfo> preprocessOsmRelation(
      OsmElement.Relation relation) {
      return preprocessOsmRelation == null ? null : preprocessOsmRelation.apply(relation);
    }
In-memory tests with fake data and profiles to ensure all features work end-to-end.
planetiler-core/src/test/java/com/onthegomap/planetiler/PlanetilerTests.java