Build a Test‑Driven REST API with Node, Express & MongoDB

Tutorial Overview

Using test‑driven development, we build a simple REST API with POST, GET, PUT, and DELETE operations.

First write tests for each endpoint, then implement the code iteratively.

Testing framework: Mocha; web framework: Express 4; database: MongoDB.

Preparation

Install Node.js, MongoDB, and configure the npm mirror. Example tools: nvm for Node, MongoDB Docker image, cnpm mirror, and supervisor for auto‑reloading.

Project Setup

Create a directory test-rest-api and enter it.

Install dependencies

npm install mocha --save-dev
npm install expect.js --save-dev 
npm install superagent --save-dev
npm install express --save
npm install mongo --save
npm install mongoskin --save
npm install body-parser --save

Create source files

express.js – API implementation

express.test.js – test suite

Write Tests

File express.test.js contains tests for POST, GET by ID, GET collection, PUT update, and DELETE.

var superagent = require('superagent')
var expect = require('expect.js')
var mongoskin = require('mongoskin')
var db = mongoskin.db('mongodb://@localhost:27017/test-rest', { safe: true })

describe('express rest api server', function() {
    // clear database before tests
    before(function() {
        db.collection('test').remove({})
    });

    var id;

    // --- test post
    it('post object', function(done) {
        superagent.post('http://localhost:3000/collections/test')
            .send({ name: 'Johns', email: '[email protected]' })
            .end(function(e, res) {
                expect(e).to.eql(null)
                expect(res.body.ops.length).to.eql(1)
                expect(res.body.ops[0]._id.length).to.eql(24)
                id = res.body.ops[0]._id
                done()
            })
    })

    // --- test get by ID
    it('retrieves an object', function(done) {
        superagent.get('http://localhost:3000/collections/test/' + id)
            .end(function(e, res) {
                expect(e).to.eql(null)
                expect(typeof res.body).to.eql('object')
                expect(res.body._id.length).to.eql(24)
                expect(res.body._id).to.eql(id)
                done()
            })
    })

    // --- test get collection
    it('retrieves a collection', function(done) {
        superagent.get('http://localhost:3000/collections/test')
            .end(function(e, res) {
                expect(e).to.eql(null)
                expect(res.body.length).to.be.above(0)
                expect(res.body.map(function(item) { return item._id })).to.contain(id)
                done()
            })
    })

    // --- test update
    it('updates an object', function(done) {
        superagent.put('http://localhost:3000/collections/test/' + id)
            .send({ name: 'Peter', email: '[email protected]' })
            .end(function(e, res) {
                expect(e).to.eql(null)
                done()
            })
    })

    // --- verify updated data
    it('checks an updated object', function(done) {
        superagent.get('http://localhost:3000/collections/test/' + id)
            .end(function(e, res) {
                expect(e).to.eql(null)
                expect(typeof res.body).to.eql('object')
                expect(res.body._id.length).to.eql(24)
                expect(res.body._id).to.eql(id)
                expect(res.body.name).to.eql('Peter')
                done()
            })
    })

    // --- test delete
    it('removes an object', function(done) {
        superagent.del('http://localhost:3000/collections/test/' + id)
            .end(function(e, res) {
                expect(e).to.eql(null)
                expect(res.body.msg).to.eql('success')
                done()
            })
    })
})

Run tests

./node_modules/mocha/bin/mocha express.test.js

Initially all tests fail because the API has not been implemented yet.

Implement API

File express.js starts with basic setup, connects to MongoDB, and defines a root route.

var express = require('express'),
    mongoskin = require('mongoskin'),
    bodyParser = require('body-parser');

var app = express();
app.use(bodyParser());

var db = mongoskin.db('mongodb://@localhost:27017/test-rest', {safe:true});

app.param('collectionName', function(req, res, next, collectionName){
    req.collection = db.collection(collectionName);
    return next();
});

app.get('/', function(req, res) {
    res.send('欢迎');
});

// --- feature code added later

app.listen(3000);

Run with node express.js or supervisor express.js for automatic reload.

Add POST endpoint

app.post('/collections/:collectionName', function(req, res, next) {
    req.collection.insert(req.body, {}, function(e, results){
        if (e) return next(e);
        res.send(results);
    });
});

Run tests again; the POST test now passes.

Add GET by ID

app.get('/collections/:collectionName/:id', function(req, res, next) {
    req.collection.findById(req.params.id, function(e, result){
        if (e) return next(e);
        res.send(result);
    });
});

Run tests; GET by ID passes.

Add GET collection

app.get('/collections/:collectionName', function(req, res, next) {
    req.collection.find({}, {limit:10, sort:[['_id',-1]]}).toArray(function(e, results){
        if (e) return next(e);
        res.send(results);
    });
});

Run tests; collection GET passes.

Add PUT update

app.put('/collections/:collectionName/:id', function(req, res, next) {
    req.collection.updateById(req.params.id, {$set:req.body}, function(e, result){
        if (e) return next(e);
        res.send(result);
    });
});

Run tests; update passes.

Add DELETE

app.del('/collections/:collectionName/:id', function(req, res, next) {
    req.collection.removeById(req.params.id, function(e, result){
        if (e) return next(e);
        res.send((result===1)?{msg:'success'}:{msg:'error'});
    });
});

Run final tests; all six tests pass and the API is complete.

Conclusion

This example demonstrates how to develop a Node.js/Express REST service using a test‑driven approach.