diff --git a/src/app/datasources/helpers/modeldefs.service.spec.ts b/src/app/datasources/helpers/modeldefs.service.spec.ts
new file mode 100644
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+++ b/src/app/datasources/helpers/modeldefs.service.spec.ts
@@ -0,0 +1,83 @@
+/*
+ * Copyright 2017-present Open Networking Foundation
+
+ * 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.
+ */
+
+import * as angular from 'angular';
+import 'angular-mocks';
+import 'angular-ui-router';
+import {XosModeldefsCache, IXosModeldefsCache} from './modeldefs.service';
+import {IXosModel} from './model-discoverer.service';
+
+describe('The XosModeldefsCache service', () => {
+  let service;
+
+  beforeEach(() => {
+    angular
+      .module('test', [])
+      .service('XosModeldefsCache', XosModeldefsCache);
+
+    angular.mock.module('test');
+  });
+
+  beforeEach(angular.mock.inject((XosModeldefsCache: IXosModeldefsCache) => {
+    service = XosModeldefsCache;
+  }));
+
+  beforeEach(() => {
+    service['xosModelDefs'] = [];
+  });
+
+  describe('the cache method', () => {
+
+    const modelDef: IXosModel = {
+      fields: [
+        {name: 'id', type: 'number'},
+        {name: 'foo', type: 'string'}
+      ],
+      relations: [],
+      name: 'Node',
+      app: 'core',
+      description: '',
+      verbose_name: ''
+    };
+    it('should add a modelDefs', () => {
+      service.cache(modelDef);
+      expect(service['xosModelDefs'].length).toBe(1);
+    });
+
+    it('should not add a modelDefs twice', () => {
+      service.cache(modelDef);
+      service.cache(modelDef);
+      expect(service['xosModelDefs'].length).toBe(1);
+    });
+  });
+
+  it('should get the service name from the app name', () => {
+    expect(service.serviceNameFromAppName('services.vsg')).toBe('vsg');
+  });
+
+  describe('the get method', () => {
+    it('should retrieve a model definition from local cache', () => {
+      const model = {
+        name: 'Node',
+        app: 'core'
+      };
+      service['xosModelDefs'] = [
+        model
+      ];
+      expect(service.get('Node')).toEqual(model);
+    });
+  });
+});