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Shwetabh Shekhar
Shwetabh Shekhar

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Generating Meaningful Test Data Using Faker

Whether you are building an API or writing tests for features that process massive datasets, meaningful test data is always a necessity. How do we fill this need? Faker is the answer.

What is Faker?

Faker is a library that can be used to generates a humongous amount of realistic fake data in Node.js and the browser. It is also available in a variety of other languages such as Python, Perl, Ruby, and C#. This article, however, will focus entirely on the Node.js flavor of Faker.

You can see a live demonstration of faker here.

Generating Data using Faker

Let's consider a use case where we want to store personal information in a CSV file with the following fields:

  • First Name
  • Last Name
  • Address(City, State, Zip Code, Country)
  • Phone Number
  • Email

And we need 100,000 such records (meaningful). Stop for a moment and think how would you have generated this? This is where Faker comes into play.

Generating CSV Datasets

Initialize your node project and Install faker:

npm i faker
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Include the dependencies in your project.

const faker = require('faker');
const fs = require('fs');
const _ = require('lodash');
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Define your headers for CSV based on the schema:

//define the headers of your csv file.
//define the object literal that would store the functions for each index
//faker generates new data for every call
let csvHeaders = {
    STREET_ADDRESS: faker.address.streetAddress(),
    STATE: faker.address.state(),
    ZIP_CODE: faker.address.zipCode(),
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I am using streams, given we are writing input into output sequentially.

// open write stream
let stream = fs.createWriteStream("huge-csv.csv");
// write the header line.
stream.write(Object.keys(csvHeaders).toString()+ "\n");
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Create the 100,000 record CSV file.

//write the body
let csvBody = [];
for (let i = 0; i < 1000000; i++) {
    _.forEach(csvHeaders, function(value, key){
    //console.log(csvBody.toString(), 'CSV BODY');
    stream.write(csvBody.toString()+ "\n");
    csvBody = [];

// close the stream
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Generating JSON Datasets

The process of generating the JSON file remains more or less the same with minor tweaks. I will leave that as an exercise. The code is available at my github repository.

Other Features and API Methods of Faker

I have only used a subset of the supported API methods in the above example. The faker.js can generate fake data for various other areas, including commerce, company, date, finance, image, random, etc.

const faker = require('faker');

# Jobs
let jobTitle =;

let jobArea =;

# dates

let futureDate =;

let recentDate =;

let weekday =;

# random values
let number = faker.random.number();

let uuid = faker.random.uuid();

let word = faker.random.word();

let words = faker.random.words(6);

# and so on...
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You can even use it directly in the browser as well.

<script src = "faker.js" type = "text/javascript"></script>
  var randomName =; // Caitlyn Kerluke
  var randomEmail =; //
  var randomCard = faker.helpers.createCard(); // random contact card containing many properties
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Fake data is extremely useful when building and testing our application and Faker can help us with that. For a complete list of supported APIs, visit this link. Have you used Faker? How was your experience?

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