test(06-mongoose): add missing tests for controller

sample/06-mongoose/src/cats/cats.controller.spec.ts

@@ -7,6 +7,8 @@ import { Types } from 'mongoose';
 const catsServiceMock = {
   create: jest.fn(),
   findAll: jest.fn(),
+  findOne: jest.fn(),
+  delete: jest.fn(),
 };
 
 describe('Cats Controller', () => {

sample/06-mongoose/src/cats/cats.service.ts

@@ -21,7 +21,7 @@ export class CatsService {
     return this.catModel.findOne({ _id: id }).exec();
   }
 
-  async delete(id: string) {
+  async delete(id: string): Promise<Cat> {
     const deletedCat = await this.catModel
       .findByIdAndRemove({ _id: id })
       .exec();