Testing with NodeJS

myFunction.ts

export function sum(a: number,b: number): number{
	return a + b;
}

myFunction.unit.spec.ts

import { sum } from './myFunction.ts';

describe('Testing sum function', () => {
	it('Should add two numbers correctly', () => {
		// Arrange
		const a: number = 4;
		const b: number = 1;
		//Act
		const result = sum(a, b);
		//Assert
		expect(result).toBe(5);
	})
})

user.integration.spec.ts

import * as request from 'supertest';
import app from '../server.ts';

describe('User', () => {
	describe('Create user endpoint', () => {
		it('Should return 201 HTTP status code and new user id', async () => {
			const response = await request(app)
					.post('/api/user')
					.send({
						email: 'test@email.com',
						password: 'supersecurepassword'
					})
			expect(response.statusCode).toEqual(201);
			expect(response.body).toEqual('new-user-id')
		})
		it('Should return an error message if parameters are missing', async () => {
			const response = await request(app)
					.post('/api/user')
					.send({});
			expect(response.statusCode).toEqual(422);
			expect(response.body).toEqual('You must enter a valid email and password.')
		})
	})
})

user.service.ts

import { DatabaseUtils } from '../utils/database.ts';
import { CreateUserDto } from '../dtos/user.ts';

export default class UserService{
	databaseUtils: DatabaseUtils;
	constructor(){
		this.databaseUtils = new DatabaseUtils();
	}

	public async createUser(
		body: CreateUserDto
	): Promise<string>{
		if(!body.email || !body.password){
			throw new Error('You must enter your email and password');
		}
		const newUserId = await this.databaseUtils.createUser(body);
		return newUserId;
	}
}

user.service.unit.spec.ts

describe('User Service class', () => {
	const userService = new UserService();

	describe('createUser method', () => {
		it('Should throw an error if email and password are not sent', async () => {
			const bodySent = {};
			await expect(userService.createUser(bodySent)).rejects.toThrowError(
				new Error('You must enter your email and passowrd')
			);
		})
		it('Should return a string if user is created', async () => {
			//Arrange
			const body: CreateUserDto = {
				email = 'test@email.com',
				password = 'supersecurepassword'
			};
			jest
				.spyOn(userService.databaseUtils, 'createUser')
				.mockResolvedValueOnce('created-user-id');
			//Act
			const serviceResponse = await userService.createUser(body);
			//Assert
			expect(serviceResponse).toEqual('created-user-id');
		})
	})
})