@Override
      public Map<String, List<VectorTile.Feature>> postProcessTileFeatures(TileCoord tileCoord,
        Map<String, List<VectorTile.Feature>> layers) {
        List<VectorTile.Feature> features = new ArrayList<>();
        features.addAll(layers.get("a"));
        features.addAll(layers.get("b"));
        return Map.of("c", features);
      }
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