Index: /trunk/test/functional/org/openstreetmap/josm/gui/mappaint/StyleCacheTest.java
===================================================================
--- /trunk/test/functional/org/openstreetmap/josm/gui/mappaint/StyleCacheTest.java	(revision 11214)
+++ /trunk/test/functional/org/openstreetmap/josm/gui/mappaint/StyleCacheTest.java	(revision 11215)
@@ -9,5 +9,7 @@
 import java.io.File;
 import java.io.InputStream;
+import java.util.IdentityHashMap;
 
+import org.junit.Assert;
 import org.junit.BeforeClass;
 import org.junit.Test;
@@ -16,4 +18,5 @@
 import org.openstreetmap.josm.data.Bounds;
 import org.openstreetmap.josm.data.osm.DataSet;
+import org.openstreetmap.josm.data.osm.OsmPrimitive;
 import org.openstreetmap.josm.data.osm.visitor.paint.Rendering;
 import org.openstreetmap.josm.data.osm.visitor.paint.StyledMapRenderer;
@@ -22,18 +25,8 @@
 import org.openstreetmap.josm.io.Compression;
 import org.openstreetmap.josm.io.OsmReader;
+import org.openstreetmap.josm.tools.Pair;
 
 /**
  * Test {@link StyleCache}.
- *
- * Verifies, that the intern pool is not growing when repeatedly rendering the
- * same set of primitives (and clearing the calculated styles each time).
- *
- * If it grows, this is an indication that the {@code equals} and {@code hashCode}
- * implementation is broken and two identical objects are not recognized as equal
- * or produce different hash codes.
- *
- * The opposite problem (different objects are mistaken as equal) has more visible
- * consequences for the user (wrong rendering on the map) and is not recognized by
- * this test.
  */
 public class StyleCacheTest {
@@ -46,4 +39,5 @@
     private static NavigatableComponent nc;
     private static DataSet dsCity;
+    private static DataSet dsCity2;
 
     @BeforeClass
@@ -64,8 +58,25 @@
             dsCity = OsmReader.parseDataSet(fisC, NullProgressMonitor.INSTANCE);
         }
+        try (
+            InputStream fisC = Compression.getUncompressedFileInputStream(new File("data_nodist/neubrandenburg.osm.bz2"));
+        ) {
+            dsCity2 = OsmReader.parseDataSet(fisC, NullProgressMonitor.INSTANCE);
+        }
     }
 
+    /**
+     * Verifies, that the intern pool is not growing when repeatedly rendering the
+     * same set of primitives (and clearing the calculated styles each time).
+     *
+     * If it grows, this is an indication that the {@code equals} and {@code hashCode}
+     * implementation is broken and two identical objects are not recognized as equal
+     * or produce different hash codes.
+     *
+     * The opposite problem (different objects are mistaken as equal) has more visible
+     * consequences for the user (wrong rendering on the map) and is not recognized by
+     * this test.
+     */
     @Test
-    public void testStyleCacheInternPool() throws Exception {
+    public void testStyleCacheInternPool() {
         Bounds bounds = new Bounds(53.56, 13.25, 53.57, 13.26);
         Rendering visitor = new StyledMapRenderer(g, nc, false);
@@ -83,3 +94,43 @@
         }
     }
+
+    /**
+     * Verifies, that the number of {@code StyleElementList} instances stored
+     * for all the rendered primitives is actually low (as intended).
+     *
+     * Two primitives with the same style should share one {@code StyleElementList}
+     * instance for the cached style elements. This is verified by counting all
+     * the instances using {@code A == B} identity.
+     */
+    @Test
+    public void testStyleCacheInternPool2() {
+        Bounds bounds = new Bounds(53.56, 13.25, 53.57, 13.26);
+        Rendering visitor = new StyledMapRenderer(g, nc, false);
+        nc.zoomTo(bounds);
+        visitor.render(dsCity2, true, bounds);
+
+        IdentityHashMap<StyleElementList, Integer> counter = new IdentityHashMap<>();
+        int noPrimitives = 0;
+        for (OsmPrimitive osm : dsCity2.allPrimitives()) {
+            // primitives, that have been rendered, should have the cache populated
+            if (osm.mappaintStyle != null) {
+                noPrimitives++;
+                Pair<StyleElementList, Range> p = osm.mappaintStyle.getWithRange(nc.getDist100Pixel(), false);
+                StyleElementList sel = p.a;
+                Assert.assertNotNull(sel);
+                Integer k = counter.get(sel);
+                if (k == null) {
+                    k = 0;
+                }
+                counter.put(sel, k + 1);
+            }
+        }
+        int EXPECTED_NO_PRIMITIVES = 4298; // needs to be updated if data file or bbox changes
+        Assert.assertEquals(
+                "The number of rendered primitives should be " + EXPECTED_NO_PRIMITIVES,
+                EXPECTED_NO_PRIMITIVES, noPrimitives);
+        Assert.assertTrue(
+                "Too many StyleElementList instances, they should be shared using the StyleCache",
+                counter.size() < 100);
+    }
 }