Testing POST with request body in Express

Introduction

We test POST requests with a body to make sure our server correctly receives and processes data sent by users or other apps.

When you want to check if your server saves new user info sent via a form.

When you need to verify that your API accepts and handles data correctly.

When you want to confirm that your server responds properly after receiving data.

When you want to catch errors if the data sent is missing or wrong.

When you want to automate testing to avoid manual checks every time you change code.

Syntax

Express

request.post('/path').send({ key: 'value' }).expect(statusCode)

Use .send() to include the request body as an object.

Use testing libraries like supertest with Express to simulate requests.

Examples

Sends a POST request to '/users' with a JSON body containing a name, expecting a 201 Created response.

Express

request.post('/users').send({ name: 'Alice' }).expect(201)

Tests login by sending username and password, expecting a 200 OK response.

Express

request.post('/login').send({ username: 'bob', password: '1234' }).expect(200)

Sample Program

This Express app has a POST route '/greet' that expects a JSON body with a 'name'. The test sends { name: 'Sam' } and expects a 200 response with a greeting message. The test prints the message from the response.

Express

import express from 'express';
import request from 'supertest';

const app = express();
app.use(express.json());

app.post('/greet', (req, res) => {
  const { name } = req.body;
  if (!name) {
    return res.status(400).send({ error: 'Name is required' });
  }
  res.status(200).send({ message: `Hello, ${name}!` });
});

// Test
(async () => {
  const response = await request(app)
    .post('/greet')
    .send({ name: 'Sam' })
    .expect(200);

  console.log(response.body.message);
})();

Important Notes

Always use express.json() middleware to parse JSON bodies in Express.

Use supertest to simulate HTTP requests easily in tests.

Check both status codes and response bodies to ensure your API works as expected.

Summary

Testing POST with a request body ensures your server handles incoming data correctly.

Use .send() to include data in your test requests.

Check both the response status and content to confirm correct behavior.