Test & improve the getCentroid/centroid method of collections

src/ol/geom/Collection.js

@@ -180,8 +180,12 @@ ol.geom.Collection.prototype.getCentroid = function() {
     if (len > 0) {
         goog.array.forEach(components, function(component){
             var singleCentroid = component.getCentroid();
-            sum_x += singleCentroid.getX();
+            if (goog.isDefAndNotNull(singleCentroid)) {
-            sum_y += singleCentroid.getX();
+                sum_x += singleCentroid.getX();
+                sum_y += singleCentroid.getX();
+            } else {
+                len--;
+            }
         });
         centroid = new ol.geom.Point(sum_x / len, sum_y / len);
     }

test/spec/api/geom/collection.test.js

@@ -178,6 +178,40 @@ describe("ol.geom.collection", function() {
             expect(c.components().length).toBe(0);
         });
     });
+
+    describe("the centroid method is functional", function(){
+        it("returns an instance of ol.geom.Point", function(){
+            expect(c.centroid()).toBeA(ol.geom.Point);
+        });
+
+        it("does not choke when components returns a null centroid", function(){
+            var centroid;
+            expect(
+                function(){
+                    c.add(new ol.geom.linestring([]));
+                    centroid = c.centroid();
+                }
+            ).not.toThrow();
+
+            expect(centroid).toBeA(ol.geom.Point);
+        });
+
+        it("has the expected coordinates", function(){
+            c = ol.geom.collection([
+                ol.geom.point([10,10]),
+                ol.geom.point([30,30]),
+                ol.geom.linestring([
+                    ol.geom.point([10,10]),
+                    ol.geom.point([10,30]),
+                    ol.geom.point([30,30]),
+                    ol.geom.point([30,10])
+                ])
+            ]);
+            debugger;
+            var centroid = c.centroid();
+            expect(centroid.x() + ',' + centroid.y()).toBe('20,20');
+        });
+    });
 });
 
 

test/spec/ol/geom/Collection.test.js

@@ -132,4 +132,37 @@ describe("ol.geom.Collection", function() {
         expect( components[1].getX() + ',' + components[1].getY()).toBe( '10,20' );
         expect( components[2].getX() + ',' + components[2].getY()).toBe( '30,40' );
     });
+
+    describe("the getCentroid method is functional", function(){
+        it("returns an instance of ol.geom.Point", function(){
+            expect(c.getCentroid()).toBeA(ol.geom.Point);
+        });
+
+        it("does not choke when components returns a null centroid", function(){
+            var centroid;
+            expect(
+                function(){
+                    c.addComponent(new ol.geom.LineString([]));
+                    centroid = c.getCentroid();
+                }
+            ).not.toThrow();
+
+            expect(centroid).toBeA(ol.geom.Point);
+        });
+
+        it("has the expected coordinates", function(){
+            c = new ol.geom.Collection([
+                new ol.geom.Point(10,10),
+                new ol.geom.Point(30,30),
+                new ol.geom.LineString([
+                    new ol.geom.Point(10,10),
+                    new ol.geom.Point(10,30),
+                    new ol.geom.Point(30,30),
+                    new ol.geom.Point(30,10)
+                ])
+            ]);
+            var centroid = c.getCentroid();
+            expect(centroid.getX() + ',' + centroid.getY()).toBe('20,20');
+        });
+    });
 });