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  • 6 Easy Steps to Build Node.js APIs with TDD Methodology

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    TDD (Test-Driven-Development) is getting popular day by day defining its needs in greater code testing. This process is a test which we define to get an output by applying to our library, API etc. Day by day Nodejs is now developing as a language of choice for REST API development, and Express has become as a framework of choice.



    The first step is to test your APIs you create before building an Express project. lets see how:


    STEP 1: Here, we are starting with a simple Express application that provide API functionality for addition and subtraction

    • Run following in a terminal to download example application-
    git clone ; cd tdd-for-apis # Clone the finished repository
    git checkout boilerplate # jump to the initial project code
    • Now, download dependencies that will be required further development process. Run following commands to set up test framework.
    npm install --save-dev supertest
    npm install --save-dev mocha


    Once above step is done, we will have our testing framework ready. Now the next process to create our first integration test.


    STEP 2: Creating Integration test

    • Create a directory in which you will take test a nd blank file to store test file. For that first, run following commands form root directory
    mkdir -p test/integration
    touch test/integration/test-route-addition.js


    • let ‘s, we will write an integration test, for that we have mount our route at /add and it will take 2 query string params called a and b. Our Expected output status should be 200(OK), if any values get missed or is non-integer value, then we receive status code 422 un-processable entity.

    Our test will look like:

    var supertest = require('supertest'),
    app = require('../../app');
    exports.addition_should_accept_numbers = function(done){
    exports.addition_should_reject_strings = function(done){


    • Run following command to run the subtraction test case;
    touch test/integration/test-route-subtraction.js


    • Our new code will be:
    var supertest = require('supertest'),
    assert = require('assert'),
    app = require('../../app');
    exports.addition_should_respond_with_a_numeric_result = function(done){
      .end(function(err, response){
        assert.ok(typeof response.body.result === 'number');
        return done();



    STEP 3: Run the integration tests

    • In the downloaded code, You can find the files /add and /subtract which are already mounted in app.js, their defining routes can be found in /routes directory. The 200(OK) status code will be returned by these routes, this provides starting functionality-creating failing test, then implement.

    Run following command:

    node_modules/.bin/mocha -u exports test/integration/*
     You can see all the changes for this step, including what npm does when we run `install --save-dev` on GitHub.



    STEP 4:  Make integration tests pass

    • Now Let’s implement two routes, /addition and /subtraction, this will take number and return a the result in numeric form.
    • Create lib directory with two files add.js and subtract.js, both of them will export function that will return 0 .Run the following commands:
    mkdir lib
    echo "module.exports = function(){ return 0; };" > lib/add.js
    echo "module.exports = function(){ return 0; };" > lib/subtract.js


    • Set up route handlers to use add and subtract function. In routes/add.js :
    var add = require('../lib/add');
    module.exports = function(req, res, next){
      return res.json({ result : add(req.a, req.b) });


    • Update app.js :
    app.use(function(req, res, next){
      var a = parseInt(req.query.a),
      b = parseInt(req.query.b);
      if (!a || !b || isNaN(a) || isNaN(b)){
        return res.status(422).end("You must specify two numbers as query params, A and B");
      req.a = a;
      req.b = b;
      return next();



    STEP 5: Add unit tests

    • Add unit tests to check if our addition and subtraction logic fails. Let ‘s create blank files for our addition and subtraction. Run following commands to create test files:
    mkdir test/unit
    touch test/unit/test-lib-addition.js ; touch test/unit/test-lib-subtraction.js;


    • Addition test will look like this:
    var assert = require('assert'),
    add = require('../../lib/add');
    exports.it_should_add_two_numbers = function(done){
      var result = add(1,1);
      assert.ok(result === 2);
      return done();
    exports.it_should_add_two_negative_numbers = function(done){
      var result = add(-2,-2);
      assert.ok(result === -4);
      return done();


    STEP 6: How to run tests by users:

    • Add an entry to our package.json file like,
    "scripts" : {
        "test" : "node_modules/.bin/mocha -u exports test/**/*"


    • Run our test by following command and it will show result :
     npm test
    6 Easy Steps to Build Node.js APIs with TDD Methodology

 1 Comment(s)

  • Building a web app using nodejs-express, postgresql, have constructed my orm models, controllers and some Middleware to do some fine-tuning on the database from a processed request. How do I pass parameters into the models for BDD like a username, email and password using Jasmine-node.we ll really appreciate if I can linked to a material that will guide. The ones I have couldn't help me. Am new to this. Thanks
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