diff --git a/src/app/service-graph/services/graph.extender.spec.ts b/src/app/service-graph/services/graph.extender.spec.ts
new file mode 100644
index 0000000..28ab96e
--- /dev/null
+++ b/src/app/service-graph/services/graph.extender.spec.ts
@@ -0,0 +1,47 @@
+import * as angular from 'angular';
+import 'angular-mocks';
+import 'angular-ui-router';
+import {IXosServiceGraphExtender, XosServiceGraphExtender} from './graph.extender';
+
+let service: IXosServiceGraphExtender, registerSpy;
+
+const reducer = (graph) => {
+  return graph;
+};
+
+describe('The XosServiceGraphExtender service', () => {
+
+  beforeEach(() => {
+    angular.module('xosServiceGraphExtender', [])
+      .service('XosServiceGraphExtender', XosServiceGraphExtender);
+
+    angular.mock.module('xosServiceGraphExtender');
+  });
+
+  beforeEach(angular.mock.inject((
+    XosServiceGraphExtender: IXosServiceGraphExtender,
+  ) => {
+    service = XosServiceGraphExtender;
+
+    registerSpy = spyOn(service, 'register').and.callThrough();
+  }));
+
+  it('should register a reducer for the coarse service graph', () => {
+    service.register('coarse', 'testCoarse', reducer);
+    expect(registerSpy).toHaveBeenCalled();
+    const coarseReducers = service.getCoarse();
+    expect(coarseReducers).toHaveLength(1);
+    expect(coarseReducers[0].name).toEqual('testCoarse');
+    expect(typeof coarseReducers[0].reducer).toEqual('function');
+  });
+
+  it('should register a reducer for the fine-grained service graph', () => {
+    service.register('finegrained', 'testFinegrained', reducer);
+    expect(registerSpy).toHaveBeenCalled();
+    const coarseReducers = service.getFinegrained();
+    expect(coarseReducers).toHaveLength(1);
+    expect(coarseReducers[0].name).toEqual('testFinegrained');
+    expect(typeof coarseReducers[0].reducer).toEqual('function');
+  });
+
+});