.env for jest and nest is not the same - jestjs

Question

I want to test a nest api, for that I create one file .env and for my dev I create a .env.development file.
Which I launch some test with jest my first test uses the good file: .env but the second test use the wrong file .env.development.
How I load the .env in nest :
import {Module} from '#nestjs/common';
import {ConfigService} from './config.service';
#Module({
providers: [{
provide: ConfigService,
useValue: new ConfigService(`.env${process.env.NODE_ENV}`),
}],
exports: [ConfigService],
})
export class ConfigModule {}
How I load the .env in jest :
"test:watch": "NODE_ENV='' jest --watch",
"jest": {
"displayName": {
"name": "API",
"color": "yellow"
},
"verbose": true,
"runner": "jest-serial-runner",
"testSequencer": "../src/test/sequencer.jest.js",
"moduleFileExtensions": [
"js",
"json",
"ts"
],
"rootDir": "src",
"testRegex": ".spec.ts$",
"transform": {
"^.+\\.(t|j)s$": "ts-jest"
},
"coverageDirectory": "../coverage",
"testEnvironment": "node",
"preset": "#shelf/jest-mongodb",
"setupFiles": [
"dotenv/config" <------------------------| here
]
},
The test for my .env (is ok the right .env is loaded)
describe('🛠️ tests for env file', () => {
it('should have a db_user', () => {
expect(process.env.db_user).toBeDefined();
});
it('should have a db_pass', () => {
expect(process.env.db_pass).toBeDefined();
});
it('should have a db_uri', () => {
expect(process.env.db_uri).toBeDefined();
});
it('should have a db_port', () => {
expect(process.env.db_port).toBeDefined();
});
it('should have a db_name', () => {
expect(process.env.db_name).toBeDefined();
});
});
The test that loads the wrong .env (I put a wrong ip for the db in .env.development, so the test failed)
import { Test, TestingModule } from '#nestjs/testing';
import * as request from 'supertest';
import {AppModule} from '../app.module';
// remove console.log
console.log = jest.fn();
describe('🗜️ UserController', () => {
let app;
beforeEach(async () => {
const moduleFixture: TestingModule = await Test.createTestingModule({
imports: [AppModule],
}).compile();
app = moduleFixture.createNestApplication();
await app.init();
});
/** valid test for create a admin user */
it('post /users valid test for create a admin user', () => {
return request(app.getHttpServer())
.post('/users')
.send({
jwt: '',
firstname: 'admin',
lastname: 'admin',
mail: 'admin#gmail.com',
password: 'test'
})
.expect(201);
});
});

Answer 1

It looks like there is a missing . after .env in this line:
new ConfigService(`.env${process.env.NODE_ENV}`)
However, the extra period is only needed when process.env.NODE_ENV contains a value so I would do something like:
const NODE_ENV = process.env.NODE_ENV ? `.${process.env.NODE_ENV}` : '';
//...
new ConfigService(`.env${NODE_ENV}`)
This way you will either end up with new ConfigService('.env') or new ConfigService('.env.development')