diff --git a/src/main/java/com/onthegomap/flatmap/read/Reader.java b/src/main/java/com/onthegomap/flatmap/read/Reader.java
index 7d8d8209..0175be24 100644
--- a/src/main/java/com/onthegomap/flatmap/read/Reader.java
+++ b/src/main/java/com/onthegomap/flatmap/read/Reader.java
@@ -42,7 +42,8 @@ public abstract class Reader implements Closeable {
         var featureCollectors = new FeatureCollector.Factory(config);
         var encoder = writer.newRenderedFeatureEncoder();
         FeatureRenderer renderer = new FeatureRenderer(
-          config, encoder, next
+          config,
+          rendered -> next.accept(encoder.apply(rendered))
         );
         while ((sourceFeature = prev.get()) != null) {
           featuresRead.incrementAndGet();
diff --git a/src/test/java/com/onthegomap/flatmap/TileExtentsTest.java b/src/test/java/com/onthegomap/flatmap/TileExtentsTest.java
new file mode 100644
index 00000000..53ce9ec2
--- /dev/null
+++ b/src/test/java/com/onthegomap/flatmap/TileExtentsTest.java
@@ -0,0 +1,60 @@
+package com.onthegomap.flatmap;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import com.onthegomap.flatmap.geo.GeoUtils;
+import org.junit.jupiter.api.Test;
+import org.locationtech.jts.geom.Envelope;
+
+public class TileExtentsTest {
+
+  private static final double eps = Math.pow(2, -30);
+
+  @Test
+  public void testFullWorld() {
+    TileExtents extents = TileExtents.computeFromWorldBounds(14, GeoUtils.WORLD_BOUNDS);
+    for (int z = 0; z <= 14; z++) {
+      int max = 1 << z;
+      assertEquals(0, extents.getForZoom(z).minX(), "z" + z + " minX");
+      assertEquals(max, extents.getForZoom(z).maxX(), "z" + z + " maxX");
+      assertEquals(0, extents.getForZoom(z).minY(), "z" + z + " minY");
+      assertEquals(max, extents.getForZoom(z).maxY(), "z" + z + " maxY");
+    }
+  }
+
+  @Test
+  public void topLeft() {
+    TileExtents extents = TileExtents
+      .computeFromWorldBounds(14, new Envelope(0, eps, 0, eps));
+    for (int z = 0; z <= 14; z++) {
+      assertEquals(0, extents.getForZoom(z).minX(), "z" + z + " minX");
+      assertEquals(1, extents.getForZoom(z).maxX(), "z" + z + " maxX");
+      assertEquals(0, extents.getForZoom(z).minY(), "z" + z + " minY");
+      assertEquals(1, extents.getForZoom(z).maxY(), "z" + z + " maxY");
+    }
+  }
+
+  @Test
+  public void topRight() {
+    TileExtents extents = TileExtents
+      .computeFromWorldBounds(14, new Envelope(1 - eps, 1, 0, eps));
+    for (int z = 0; z <= 14; z++) {
+      assertEquals((1 << z) - 1, extents.getForZoom(z).minX(), "z" + z + " minX");
+      assertEquals((1 << z), extents.getForZoom(z).maxX(), "z" + z + " maxX");
+      assertEquals(0, extents.getForZoom(z).minY(), "z" + z + " minY");
+      assertEquals(1, extents.getForZoom(z).maxY(), "z" + z + " maxY");
+    }
+  }
+
+  @Test
+  public void bottomLeft() {
+    TileExtents extents = TileExtents
+      .computeFromWorldBounds(14, new Envelope(0, eps, 1 - eps, 1));
+    for (int z = 0; z <= 14; z++) {
+      assertEquals(0, extents.getForZoom(z).minX(), "z" + z + " minX");
+      assertEquals(1, extents.getForZoom(z).maxX(), "z" + z + " maxX");
+      assertEquals((1 << z) - 1, extents.getForZoom(z).minY(), "z" + z + " minY");
+      assertEquals(1 << z, extents.getForZoom(z).maxY(), "z" + z + " maxY");
+    }
+  }
+}
diff --git a/src/test/java/com/onthegomap/flatmap/collections/CacheByZoomTest.java b/src/test/java/com/onthegomap/flatmap/collections/CacheByZoomTest.java
new file mode 100644
index 00000000..ffca5483
--- /dev/null
+++ b/src/test/java/com/onthegomap/flatmap/collections/CacheByZoomTest.java
@@ -0,0 +1,29 @@
+package com.onthegomap.flatmap.collections;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import com.onthegomap.flatmap.Arguments;
+import com.onthegomap.flatmap.CommonParams;
+import java.util.ArrayList;
+import java.util.List;
+import org.junit.jupiter.api.Test;
+
+public class CacheByZoomTest {
+
+  @Test
+  public void testCacheZoom() {
+    List<Integer> calls = new ArrayList<>();
+    CacheByZoom<Integer> cached = CacheByZoom.create(CommonParams.from(Arguments.of(
+      "minzoom", "1",
+      "maxzoom", "10"
+    )), i -> {
+      calls.add(i);
+      return i + 1;
+    });
+    assertEquals(3, cached.get(2));
+    assertEquals(3, cached.get(2));
+    assertEquals(6, cached.get(5));
+    assertEquals(List.of(2, 5), calls);
+  }
+
+}