How to test Models (Mongoose) in a service (NestJS) with jest - node.js

Question

I have a backend done with NestJS. In my service I inject two Mongoose Models. I use Jest to test the service.
Models are declared as is and injected into the module:
quizes.providers.ts
import { Connection } from 'mongoose';
import { QuizSchema } from './schemas/quiz.schema';
export const quizesProviders = [
{
provide: 'CLASS_MODEL',
useFactory: (connection: Connection) => connection.model('Quiz', QuizSchema),
inject: ['DATABASE_CONNECTION'],
},
];
users.providers.ts
import { Connection } from 'mongoose';
import { UserSchema } from './schemas/user.schema';
export const usersProviders = [
{
provide: 'USER_MODEL',
useFactory: (connection: Connection) => connection.model('User', UserSchema),
inject: ['DATABASE_CONNECTION'],
},
];
Example of module:
quizes.module.ts
import { Module } from '#nestjs/common';
import { QuizesController } from './quizes.controller';
import { QuizesService } from './quizes.service';
import { quizesProviders } from './quizes.providers';
import { usersProviders } from '../auth/users.providers';
import { DatabaseModule } from 'src/database.module';
import { AuthModule } from 'src/auth/auth.module';
#Module({
imports: [DatabaseModule, AuthModule],
controllers: [QuizesController],
providers: [QuizesService,
...quizesProviders, ...usersProviders]
})
export class QuizesModule {}
Then in my service, I inject models:
quizes.service.ts
#Injectable()
export class QuizesService {
constructor(
#Inject('CLASS_MODEL')
private classModel: Model<Quiz>,
#Inject('USER_MODEL')
private userModel: Model<User>
) {}
In my quizes.spec.ts (jest) I began to do things like that. It compiles but doesn't work:
import { Test } from '#nestjs/testing';
import * as mongoose from 'mongoose';
import { User } from 'src/auth/user.interface';
import { Quiz } from './quiz.interface';
import { databaseProviders } from '../database.providers';
const USER_MODEL:mongoose.Model<User> = mongoose.model('User', UserSchema);
const CLASS_MODEL:mongoose.Model<Quiz> = mongoose.model('Quiz', QuizSchema);
const mockingQuizModel = () => {
find: jest.fn()
}
const mockingUserModel = () => {
find: jest.fn()
}
const mockUser = {
username: 'Test user'
}
describe('QuizesService', () => {
let quizesService;
let userModel , classModel;
beforeEach(async () => {
const module = await Test.createTestingModule({
providers: [QuizesService, ...usersProviders, ...quizesProviders,...databaseProviders,
{provide: USER_MODEL, useFactory: mockingUserModel},
{provide: CLASS_MODEL, useFactory: mockingQuizModel},
],
}).compile();
quizesService = await module.get<QuizesService>(QuizesService);
classModel = await module.get<mongoose.Model<Quiz>>(CLASS_MODEL)
userModel = await module.get<mongoose.Model<User>>(USER_MODEL)
})
describe('getAllQuizes', ()=> {
it('get all quizes', () => {
expect(userModel.find).not.toHaveBeenCalled();
})
})
})
userModel is undefined and the test does not exit.

Answer 1

Use the getModelToken function as defined in NestJS official: https://docs.nestjs.com/v6/
Techniques -> Mongo (Scroll down to Testing section)
Then your code should look a bit like this:
import { getModelToken } from '#nestjs/mongoose';
const mockRepository = {
find() {
return {};
}
};
const module = await Test.createTestingModule({
providers: [ ...,
{provide: getModelToken('CLASS_MODEL'), useValue: mockRepository,},
{provide: getModelToken('USER_MODEL'), useValue: mockRepository,},
],
...

Answer 2

Fixed
You should not use await for module.get
quizesService = module.get<QuizesService>(QuizesService);
clientClassModel = module.get(getModelToken('CLASS_MODEL'))
clientUserModel = module.get(getModelToken('USER_MODEL'))

Answer 3

The setup of the test suite was ok but not the test
I test the service getAllQuizes method
Here is the service
#Injectable()
export class QuizesService {
constructor(
#InjectModel('CLASS_MODEL')
private classModel: Model<Quiz>,
#InjectModel('USER_MODEL')
private userModel: Model<User>
) {}
async getAllQuizes(user: User) : Promise<Quiz[]> {
// console.log(user);
let userId;
try {
const userEntity = await this.userModel.find({username: user.username}).exec();
userId = userEntity[0]._id;
} catch (error) {
throw new NotFoundException('user not found');
}
return await this.classModel.find({user: userId}).exec();
}
Here is the test
it('get all quizes', async () => {
clientUserModel.find.mockResolvedValue('user1');
clientClassModel.find.mockResolvedValue([{title: 'test', description: 'test'}])
expect(clientUserModel.find).not.toHaveBeenCalled();
expect(clientClassModel.find).not.toHaveBeenCalled();
const result = quizesService.getAllQuizes(mockUser);
expect(clientUserModel.find).toHaveBeenCalled();
expect(clientClassModel.find).toHaveBeenCalled();
expect(result).toEqual([{title: 'test', description: 'test'}]);
})
My test is false because the assertion expect(clientClassModel.find).toHaveBeenCalled() is false
Whereas in my service I have a first call on find method of the user model, and a second call on the find method of the class model

Answer 4

Finally tests pass
describe("getAllQuizes", () => {
it("get all quizes, user not found", async () => {
clientUserModel.find.mockRejectedValue("user not found");
clientClassModel.find.mockResolvedValue([
{ title: "test", description: "test" },
]);
expect(clientUserModel.find).not.toHaveBeenCalled();
expect(clientClassModel.find).not.toHaveBeenCalled();
const result = quizesService.getAllQuizes(mockUser).catch((err) => {
expect(err.message).toEqual("user not found");
});
expect(clientUserModel.find).toHaveBeenCalled();
});
it("get all quizes, find quizzes", async () => {
clientUserModel.find.mockReturnValue({
_id: "1234",
username: "Test user",
});
clientClassModel.find.mockResolvedValue([
{ title: "test", description: "test" },
]);
expect(clientUserModel.find).not.toHaveBeenCalled();
expect(clientClassModel.find).not.toHaveBeenCalled();
const result = quizesService.getAllQuizes(mockUser).then((state) => {
expect(clientUserModel.find).toHaveBeenCalled();
expect(clientClassModel.find).toHaveBeenCalled();
expect(state).toEqual([{ title: "test", description: "test" }]);
});
//
});
});