Fix OGCCollection#reduceFromMulti and add test

src/main/java/com/esri/core/geometry/ogc/OGCMultiPolygon.java

@@ -139,7 +139,7 @@ public OGCGeometry convertToMulti()
 	public OGCGeometry reduceFromMulti() {
 		int n = numGeometries();
 		if (n == 0) {
-			return new OGCLineString(new Polygon(polygon.getDescription()), 0, esriSR);
+			return new OGCPolygon(new Polygon(polygon.getDescription()), 0, esriSR);
 		}
 
 		if (n == 1) {

src/test/java/com/esri/core/geometry/TestOGCReduceFromMulti.java

@@ -0,0 +1,80 @@
+/*
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.esri.core.geometry;
+
+import org.junit.Test;
+
+import static com.esri.core.geometry.ogc.OGCGeometry.fromText;
+import static java.lang.String.format;
+import static org.junit.Assert.assertEquals;
+
+public class TestOGCReduceFromMulti
+{
+    @Test
+    public void testPoint()
+    {
+        assertReduceFromMulti("POINT (1 2)", "POINT (1 2)");
+        assertReduceFromMulti("POINT EMPTY", "POINT EMPTY");
+        assertReduceFromMulti("MULTIPOINT (1 2)", "POINT (1 2)");
+        assertReduceFromMulti("MULTIPOINT (1 2, 3 4)", "MULTIPOINT ((1 2), (3 4))");
+        assertReduceFromMulti("MULTIPOINT EMPTY", "POINT EMPTY");
+    }
+
+    @Test
+    public void testLineString()
+    {
+        assertReduceFromMulti("LINESTRING (0 0, 1 1, 2 3)", "LINESTRING (0 0, 1 1, 2 3)");
+        assertReduceFromMulti("LINESTRING EMPTY", "LINESTRING EMPTY");
+        assertReduceFromMulti("MULTILINESTRING ((0 0, 1 1, 2 3))", "LINESTRING (0 0, 1 1, 2 3)");
+        assertReduceFromMulti("MULTILINESTRING ((0 0, 1 1, 2 3), (4 4, 5 5))", "MULTILINESTRING ((0 0, 1 1, 2 3), (4 4, 5 5))");
+        assertReduceFromMulti("MULTILINESTRING EMPTY", "LINESTRING EMPTY");
+    }
+
+    @Test
+    public void testPolygon()
+    {
+        assertReduceFromMulti("POLYGON ((0 0, 1 0, 1 1, 0 0))", "POLYGON ((0 0, 1 0, 1 1, 0 0))");
+        assertReduceFromMulti("POLYGON EMPTY", "POLYGON EMPTY");
+        assertReduceFromMulti("MULTIPOLYGON (((0 0, 1 0, 1 1, 0 0)))", "POLYGON ((0 0, 1 0, 1 1, 0 0))");
+        assertReduceFromMulti("MULTIPOLYGON (((0 0, 1 0, 1 1, 0 0)), ((2 2, 3 2, 3 3, 2 2)))", "MULTIPOLYGON (((0 0, 1 0, 1 1, 0 0)), ((2 2, 3 2, 3 3, 2 2)))");
+        assertReduceFromMulti("MULTIPOLYGON EMPTY", "POLYGON EMPTY");
+    }
+
+    @Test
+    public void testGeometryCollection()
+    {
+        assertReduceFromMulti(gc("POINT (1 2)"), "POINT (1 2)");
+        assertReduceFromMulti(gc("MULTIPOINT (1 2)"), "POINT (1 2)");
+        assertReduceFromMulti(gc(gc("POINT (1 2)")), "POINT (1 2)");
+        assertReduceFromMulti(gc("POINT EMPTY"), "POINT EMPTY");
+
+        assertReduceFromMulti(gc("LINESTRING (0 0, 1 1, 2 3)"), "LINESTRING (0 0, 1 1, 2 3)");
+        assertReduceFromMulti(gc("POLYGON ((0 0, 1 0, 1 1, 0 0))"), "POLYGON ((0 0, 1 0, 1 1, 0 0))");
+
+        assertReduceFromMulti(gc("POINT (1 2), LINESTRING (0 0, 1 1, 2 3)"), gc("POINT (1 2), LINESTRING (0 0, 1 1, 2 3)"));
+
+        assertReduceFromMulti("GEOMETRYCOLLECTION EMPTY", "GEOMETRYCOLLECTION EMPTY");
+        assertReduceFromMulti(gc("GEOMETRYCOLLECTION EMPTY"), "GEOMETRYCOLLECTION EMPTY");
+    }
+
+    private void assertReduceFromMulti(String wkt, String reducedWkt)
+    {
+        assertEquals(reducedWkt, fromText(wkt).reduceFromMulti().asText());
+    }
+
+    private String gc(String wkts)
+    {
+        return format("GEOMETRYCOLLECTION (%s)", wkts);
+    }
+}