ng g service todo/todo

src/app/todo/todo.service.spec.ts

@@ -0,0 +1,16 @@
+/* tslint:disable:no-unused-variable */
+
+import { TestBed, async, inject } from '@angular/core/testing';
+import { TodoService } from './todo.service';
+
+describe('Service: Todo', () => {
+  beforeEach(() => {
+    TestBed.configureTestingModule({
+      providers: [TodoService]
+    });
+  });
+
+  it('should ...', inject([TodoService], (service: TodoService) => {
+    expect(service).toBeTruthy();
+  }));
+});

src/app/todo/todo.service.ts

@@ -0,0 +1,8 @@
+import { Injectable } from '@angular/core';
+
+@Injectable()
+export class TodoService {
+
+  constructor() { }
+
+}