Jest not closing because of Mongoose.model - node.js

Question

I am trying to create my first test with jest.
user_model_test.js
const mongoose = require('mongoose')
const User = require('../user_model')
describe('user model tests', () => {
beforeAll( async () => {
await mongoose.connect('mongodb://localhost/supertest21')
})
afterAll( async () => {
await mongoose.connection.close()
})
it("has a module", () => {
expect(User).toBeDefined()
})
})
user_model.js
const mongoose = require('mongoose')
const Schema = mongoose.Schema
const userSchema = new Schema({
username: {
type: String,
required: true
},
password: {
type: String,
required: true
},
email: {
type: String,
required: true
}
})
const User = mongoose.model('User', userSchema, 'user')
module.exports = User
When I run my test, running with --detectOpenHandles I get this error:
Jest has detected the following 1 open handle potentially keeping Jest from exiting:
● PROMISE
17 | })
18 |
> 19 | const User = mongoose.model('User', userSchema, 'user')
| ^
20 |
21 | module.exports = User
at Function.init (node_modules/mongoose/lib/model.js:970:16)
at Mongoose.Object.<anonymous>.Mongoose.model (node_modules/mongoose/lib/index.js:396:11)
at Object.<anonymous> (libs/user/user_model.js:19:23)
at Object.<anonymous> (libs/user/__tests__/user_model_test.js:3:14)
I know that there is something to do with the mongoose.model initialization.When I pass the 4th parameter to mongoose.model, to skip initialization, the promise error don't show up but the test never closes and don't show any more errors. Any ideas?

Answer 1

Using a setup file and setupFilesAfterEnv
Jest can call a "setup.js" file to run some beforeAll and afterAll functions. As ongoing Mongoose's connections keep Jest open, we will close them using the afterAll hook.
Solution
In your jest.config.js, add the following lines:
setupFilesAfterEnv: [
'<rootDir>/tests/setup.js', // <- Feel free to place this file wherever it's convinient
],
Create a setup.js file with the following code:
import { getMongoDBInstance } from '../src/bin/server.ts';
afterAll(async () => {
const mongoDB = getMongoDBInstance();
await mongoDB.connection.close();
});
Here, getMongoDBInstance is a function that returns me the instance of Mongoose I instantiate when my server boots.
let mongoDB;
async function initServer() {
...
await mongoose.connect(uristring, {
useNewUrlParser: true,
useUnifiedTopology: true,
});
mongoDB = mongoose;
...
}
export const getMongoDBInstance = () => mongoDB;
And now after all tests ran, Jest will call this function and close any MongoDB connections! You can follow the same to solve open connections with knex, or any other node ORMs.

Answer 2

Try changing await mongoose.connection.close() to await mongoose.disconnect();. Worked for me.