Tu primer prueba e2e

How to write your first test in Twen?

Writing tests for web applications is essential to ensure that your software works correctly in several cases. An excellent example is the use of Twen to write tests that simulate HTTP requests to our Node.js server, similar to what we do with tools like Postman or Insomnia. The difference is that, with Twen, we can automate and professionalize this process.

What would Insomnia or Postman do, but in an automatic way?

Programs like Insomnia or Postman allow you to make manual HTTP requests to a server to get responses. However, these are not tests as such, but simply simulations of requests. Twen, on the other hand, goes one step further. It automatically sends multiple tests to a single endpoint to verify aspects such as response status code, data validation and server connectivity. Thus, we can ensure that the application works correctly under different scenarios.

Which tool to use for end-to-end testing in Node?

To perform similar tests in an automated way in Node.js, we use Supertest. This tool is ideal for emulating HTTP requests and verifying their responses programmatically. Like Yes, Supertest is installed as a development dependency.

Installing Supertest

Open your terminal and proceed to install Supertest using the following command, making sure you are in the right working environment:

npm install --save-dev supertest

With the tool installed, we can proceed to create and test endpoints in our Express application.

How to create a basic Express server with an endpoint?

First, we will set up a simple Express application that will serve as the basis for our tests:

const express = require('express');const app = express();
app.get('/hello', (req, res) => { res.status(200).json({ name: 'Nico' });});
app.listen(9000, () => { console.log('Server is running on port 9000');});

This code creates a small Express server with an endpoint called /hello, which responds with a JSON containing a name. Now, we must prepare the tests for this server.

How to test an endpoint with Supertest?

Supertest allows us to define our tests as follows:

const request = require('supertest');
describe('Tests for endpoint /hello', () => { it('Must respond with a status 200 and an expected JSON', async () => { const response = await request(app).get('/hello'); expect(response.statusCode).toEqual(200); expect(response.body.name).toEqual('Nico'); expect(response.headers['content-type']).toMatch(/json/); });});

Explanation of the test code

1. Requests: We use request(app).get('/hello') to send a GET request to the /hello endpoint.

2. Checks (expectations):

   • We verify that the status code is 200.
   • We check that the response body contains the name 'Nico'.
   • Confirm that the content type returned is JSON.

3. Test run: To run these tests, we use the command for our test environment, which usually involves a testing tool such as jest.

npx jest

Running the above command will validate that all the tests defined in the file run correctly.

What to do if tests fail or there are asynchronous problems?

During the execution of tests, you might encounter errors if the server response does not match what is expected. Precisely, if we request a 200 status code but get a 201, for example, the test will fail. To solve this:

• Verify the expected and application status code.
• Analyze the server responses to make sure they match what is specified in the test.

In addition, it is common to encounter warnings about unfinished asynchronous processes. This problem arises when the Express server does not stop after testing. You can close these processes at the end of all tests or by modifying the configuration of your testing tools.

Automated testing is essential for modern development, so don't stop here and keep exploring tools and methodologies that ensure the quality of your software!