Added unit tests to show that the FeatureSizeFeatureCollection now de…

…legates.

Additionally adds infrastructure for testing how other FeatureCollections interact with Visitors.

src/wfs/src/test/java/org/geoserver/wfs/FeatureCollectionDelegationTest.java

@@ -0,0 +1,116 @@
+package org.geoserver.wfs;
+
+import com.vividsolutions.jts.geom.Coordinate;
+import com.vividsolutions.jts.geom.GeometryFactory;
+import com.vividsolutions.jts.geom.Point;
+import org.geoserver.feature.RetypingFeatureCollection;
+import org.geoserver.security.AccessLimits;
+import org.geoserver.security.CatalogMode;
+import org.geoserver.security.WrapperPolicy;
+import org.geoserver.security.decorators.SecuredObjects;
+import org.geoserver.test.GeoServerSystemTestSupport;
+import org.geotools.data.DataUtilities;
+import org.geotools.data.Query;
+import org.geotools.data.collection.ListFeatureCollection;
+import org.geotools.data.simple.SimpleFeatureCollection;
+import org.geotools.data.simple.SimpleFeatureSource;
+import org.geotools.factory.CommonFactoryFinder;
+import org.geotools.feature.collection.FilteringSimpleFeatureCollection;
+import org.geotools.feature.simple.SimpleFeatureBuilder;
+import org.geotools.feature.simple.SimpleFeatureTypeBuilder;
+import org.geotools.feature.visitor.CountVisitor;
+import org.geotools.feature.visitor.MaxVisitor;
+import org.junit.Assert;
+import org.junit.Before;
+import org.junit.Test;
+import org.opengis.feature.FeatureVisitor;
+import org.opengis.feature.simple.SimpleFeatureType;
+import org.opengis.filter.Filter;
+import org.opengis.util.ProgressListener;
+
+import java.util.Arrays;
+import java.util.List;
+
+public class FeatureCollectionDelegationTest extends GeoServerSystemTestSupport {
+    private final WrapperPolicy policy = WrapperPolicy.readOnlyHide(new AccessLimits(CatalogMode.HIDE));
+    private static final String FEATURE_TYPE_NAME = "testType";
+    private FeatureVisitor lastVisitor = null;
+
+    // These collections will delegate the MaxVisitor
+    // As an example, ReTypingFeatureCollections may not delegate.
+    private List<SimpleFeatureCollection> maxVisitorCollections;
+
+    // These collection will delegate the CountVisitor
+    private List<SimpleFeatureCollection> countVisitorCollections;
+
+    @Before
+    public void setUp() throws Exception {
+        lastVisitor = null;
+
+        GeometryFactory fac = new GeometryFactory();
+        Point p = fac.createPoint(new Coordinate(8, 9));
+
+        SimpleFeatureTypeBuilder builder = new SimpleFeatureTypeBuilder();
+        builder.setName(FEATURE_TYPE_NAME);
+        builder.add("geom", Point.class);
+
+        SimpleFeatureType ft = builder.buildFeatureType();
+        SimpleFeatureBuilder b = new SimpleFeatureBuilder(ft);
+        b.add(p);
+
+        ListFeatureCollection visitorCollection =
+                new ListFeatureCollection(ft) {
+                    public void accepts(FeatureVisitor visitor, ProgressListener progress) {
+                        lastVisitor = visitor;
+                    };
+
+                    @Override
+                    public SimpleFeatureCollection subCollection(Filter filter) {
+                        if (filter == Filter.INCLUDE) {
+                            return this;
+                        } else {
+                            return super.subCollection(filter);
+                        }
+                    }
+                };
+        SimpleFeatureSource featureSource = DataUtilities.source(visitorCollection);
+
+        maxVisitorCollections = Arrays.asList(
+                new FeatureSizeFeatureCollection(visitorCollection, featureSource, Query.ALL),
+                new FilteringSimpleFeatureCollection(visitorCollection, Filter.INCLUDE)
+        );
+        countVisitorCollections = Arrays.asList(
+                new FeatureSizeFeatureCollection(visitorCollection, featureSource, Query.ALL),
+                new FilteringSimpleFeatureCollection(visitorCollection, Filter.INCLUDE),
+                new RetypingFeatureCollection(visitorCollection, visitorCollection.getSchema()),
+                (SimpleFeatureCollection)SecuredObjects.secure(visitorCollection, policy)
+        );
+    }
+
+    @Test
+    public void testMaxVisitorDelegation() {
+        MaxVisitor visitor =
+                new MaxVisitor(CommonFactoryFinder.getFilterFactory2().property("value"));
+        assertOptimalVisit(visitor, maxVisitorCollections);
+    }
+
+    @Test
+    public void testCountVisitorDelegation() {
+        FeatureVisitor visitor = new CountVisitor();
+        assertOptimalVisit(visitor, countVisitorCollections);
+    }
+
+    private void assertOptimalVisit(FeatureVisitor visitor, List<SimpleFeatureCollection> collections) {
+        collections.forEach(simpleFeatureCollection -> {
+                    try {
+                        lastVisitor = null;
+                        simpleFeatureCollection.accepts(visitor, null);
+                    } catch (Exception e) {
+                        Assert.fail();
+                    }
+                    Assert.assertSame(lastVisitor, visitor);
+                }
+        );
+    }
+}
+