DEV Community

loading...
Cover image for Generating Meaningful Test Data Using Faker

Generating Meaningful Test Data Using Faker

shwetabh1 profile image Shwetabh Shekhar ・3 min read

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
Enter fullscreen mode Exit fullscreen mode

Include the dependencies in your project.

const faker = require('faker');
const fs = require('fs');
const _ = require('lodash');
Enter fullscreen mode Exit fullscreen mode

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 = {
    FIRST_NAME: faker.name.firstName(),
    LAST_NAME: faker.name.lastName(),
    STREET_ADDRESS: faker.address.streetAddress(),
    CITY: faker.address.city(),
    STATE: faker.address.state(),
    ZIP_CODE: faker.address.zipCode(),
    COUNTRY: faker.address.country(),
    VOICE_NUMBER: faker.phone.phoneNumber(),
    EMAIL_ADDRESS: faker.internet.email(),
}
Enter fullscreen mode Exit fullscreen mode

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");
Enter fullscreen mode Exit fullscreen mode

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(value);
        csvBody.push(value);
    })
    //console.log(csvBody.toString(), 'CSV BODY');
    stream.write(csvBody.toString()+ "\n");
    csvBody = [];


}
// close the stream
stream.end(); 
Enter fullscreen mode Exit fullscreen mode

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 = faker.name.jobTitle();
console.log(jobTitle);

let jobArea = faker.name.jobArea();
console.log(jobArea);

# dates

let futureDate = faker.date.future();
console.log(futureDate);

let recentDate = faker.date.recent();
console.log(recentDate);

let weekday = faker.date.weekday();
console.log(weekday);

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

let uuid = faker.random.uuid();
console.log(uuid);

let word = faker.random.word();
console.log(word);

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

# and so on...
Enter fullscreen mode Exit fullscreen mode

You can even use it directly in the browser as well.

<script src = "faker.js" type = "text/javascript"></script>
<script>
  var randomName = faker.name.findName(); // Caitlyn Kerluke
  var randomEmail = faker.internet.email(); // Rusty@arne.info
  var randomCard = faker.helpers.createCard(); // random contact card containing many properties
</script>
Enter fullscreen mode Exit fullscreen mode

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?

Discussion (0)

pic
Editor guide