How to create a mock REST api for testing in nodejs

sameer nodejs

There is a frequent requirement during api development to create a mock api quickly so that other team members can use the same to test their respective part of the project. For example front-end developers might need the api endpoints to test their designs. Rather than wait for the complete api to be finished, developers can create a mock api quickly for testing. This nodejs module by typicode helps front-end developers who need a quick back-end for prototyping and mocking REST apis!

Installation

As usual install the nodejs module using npm.

$ npm install -g json-server

Create a db.json file that mocks a api endpoint. A sample is shown below. The code is in JSON format and include some basic information for 2 users.

{
  "users": [
    {
      "id": 1,
      "first_name": "john",
      "last_name": "doe"
    },
    {
      "id": 2,
      "first_name": "jane",
      "last_name": "roe"
    }
  ]
}

Now start the JSON server.

$ json-server --watch db.json

Now browse to the following url.

http://localhost:3000/users

You should see the following output in your browser.

[
  {
    "id": 1,
    "first_name": "john",
    "last_name": "doe"
  },
  {
    "id": 2,
    "first_name": "jane",
    "last_name": "roe"
  }
]

With the following url.

http://localhost:3000/users/2

You will get the following JSON reply.

{
  "id": 2,
  "first_name": "jane",
  "last_name": "roe"
}

You can also test using cURL although I prefer the Chrome Postman app.

$ curl -X GET http://localhost:3000/users/2

You can also integrate the ‘json-server’ module into nodejs scripts.

var jsonServer = require('json-server');
 
var server = jsonServer.create();
var router = jsonServer.router('db.json');
server.use(router);
server.listen(3000);

Based on the previous db.json file, below are all the default routes.

GET    /users
GET    /users/1
POST   /users
PUT    /users/1
PATCH  /users/1
DELETE /users/1

Note that if you make POST, PUT, PATCH or DELETE requests, changes will be automatically and safely saved to db.json. For example if you make a POST request like the following a new user will be added with only the ‘id’ field auto-incremented with the next available id number.

Note that if you manually make any changes to the db.json file you need to restart the json-server program for the new content in the file to take effect. 

http://localhost:3000/users

The content in the db.json file after the request will be the following.

{
  "users": [
    {
      "id": 1,
      "first_name": "john",
      "last_name": "doe"
    },
    {
      "id": 2,
      "first_name": "jane",
      "last_name": "roe"
    },
    {
      "id": 3
    }
  ]
}

Apso, navigating to the home page will display a nice welcome screen.

http://localhost:3000/

Filtering resources

You can filter resources like the following using GET.

http://localhost:3000/users?first_name=jane
http://localhost:3000/users?id=1

To make a full-text search on resources, add q.

http://localhost:3000/users?q=oe

For my project purpose the above was all that was required. The library however offers many more features of which more information can be found at its home page.

api rest

sameer