Util now has a spec.

@@ -5,7 +5,7 @@ define(function(require) {
         var result = filterFunc(obj);
         var ptr = startPtr;
         while (true) {
-            result = _.extend(result, filterFunc(_.result(ptr, fieldName)));
+            result = _.defaults(result, filterFunc(_.result(ptr, fieldName)));
             if (ptr === endPtr) {
                 break;
             }

+define(function(require) {
+    'use strict';
+    var _ = require('underscore');
+    var Backbone = require('backbone');
+    var Util = require('solr/model/Util');
+
+    var BaseModel = Backbone.Model.extend({}, {
+        staticProps: function() {
+            return {
+                hardCoded: 74,
+                override: 75,
+            };
+        },
+        staticSets: ['hardCoded', 'override'],
+    });
+    var SubModel = BaseModel.extend({}, {
+        staticProps: {
+            override: 76,
+            newConstant: 77,
+        },
+        staticSets: function() {
+            return ['override', 'newConstant'];
+        },
+    });
+    describe('Util', function() {
+        it('loads', function() {
+            expect(Util).toBeDefined();
+        });
+
+        it('exported items', function() {
+            var keys = {};
+            _.each(Util, function(value, key) {
+                keys[key] = true;
+            });
+            expect(keys).toEqual({
+                getField: true,
+                setField: true,
+                getItemKeyAccessor: true,
+                mergeStaticProps: true,
+                mergeStaticSets: true,
+            });
+        });
+        describe('methods', function() {
+            var pojo, bb, emptyBB;
+            beforeEach(function() {
+                pojo = {a: 1, b: 2, key: 'TheKey'};
+                bb = new BaseModel(pojo);
+                emptyBB = new SubModel();
+            });
+            it('setField only modifies given', function() {
+                var r = Util.setField(pojo, 'a', 100);
+                expect(pojo).toEqual({a: 100, b: 2, key: 'TheKey'});
+                expect(r).toBe(100);
+            });
+            it('setField adds new', function() {
+                var r = Util.setField(pojo, 'c', 42);
+                expect(pojo).toEqual({a: 1, b: 2, c: 42, key: 'TheKey'});
+                expect(r).toBe(42);
+            });
+            it('getField returns value', function() {
+                var r = Util.getField(pojo, 'b');
+                expect(pojo).toEqual({a: 1, b: 2, key: 'TheKey'});
+                expect(r).toBe(2);
+            });
+            it('getField returns undefined', function() {
+                var r = Util.getField(pojo, 'c');
+                expect(pojo).toEqual({a: 1, b: 2, key: 'TheKey'});
+                expect(r).toBe(undefined);
+            });
+            it('itemKeyAccessor returns value', function() {
+                var r = Util.getItemKeyAccessor(bb);
+                expect(r).toBe('TheKey');
+            });
+            it('itemKeyAccessor returns undefined', function() {
+                var r = Util.getItemKeyAccessor(emptyBB);
+                expect(r).toBe(undefined);
+            });
+            it('mergeStaticProps', function() {
+                var r = Util.mergeStaticProps(SubModel, Backbone.Model, {'default': 1}, 'staticProps');
+                expect(r).toEqual({default: 1, hardCoded: 74, override: 76, newConstant: 77});
+            });
+            it('mergeStaticSets', function() {
+                var r = Util.mergeStaticSets(SubModel, Backbone.Model, ['default'], 'staticSets');
+                var keys = {};
+                _.each(r, function(value) {
+                    keys[value] = true;
+                });
+                expect(keys).toEqual({default: true, hardCoded: true, override: true, newConstant: true});
+            });
+        });
+    });
+});