Feb 24, 2024 • 4 min read

Node Fake Data

A quick guide on generating test data. If you have used the Pet Theory lab, this should be familar, but if not here is the code.

The general idea is to create a csv based on made up dataset. To do this, use the Fakerjs package and write the output as csv records.

If you have not worked with Fakerjs before, this is a nice short cut to get to grips with the Firestore API.

Requirements:

Node.js installation
Fakerjs package

Overview

In this blog post learn how to create fake test data in the CSV format.

Application Code

The template application will be based on Node.js. If you are unfamiliar with Node.js, this is a standard step to create the files required.

The package.json file provides the information relating to packages used and general descriptions. In addition it has a helpful script section, for testing that can be generalised.

Add a package.json

            NODE_TYPE // bash
        
{
  "name": "create-td",
  "version": "1.0.0",
  "description": "This is lab01 of the Pet Theory labs",
  "main": "index.js",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "keywords": [],
  "author": "Rich Rose",
  "license": "MIT",
  "devDependencies": {
    "@faker-js/faker": "^8.4.1"
  }
}

Create an index.js file

The code is required to do the following things:

Include package dependencies
Add a createTestData function

Run app

The npm packages are required:

NODE_TYPE // bash

npm install --save-dev @faker-js/faker

Run the application

NODE_TYPE // bash

node index.js 10

Expected Output:

NODE_TYPE // bash

Created file customers_10.csv containing 10 records.

Package Dependencies

A declaration for generating data.

            NODE_TYPE // JavaScript
        

const fs        = require("fs");
const { faker } = require("@faker-js/faker");

Validate Command Line Arguments

The application expects the name of a CSV file to be added. If a filename is not present, the application will exit.

            NODE_TYPE // javascript
        
recordCount = parseInt(process.argv[2]);

if (process.argv.length != 3 || recordCount < 1 || isNaN(recordCount)) {
	console.error("Include the number of test data records to create. Example:");
	console.error("    node createTestData.js 100");
	process.exit(1);
}

createTestData(recordCount);

Custom Data Schema

Use the fakerjs package to create fake data. The data will be written to a filename with the extension csv.

A record of the following schema is created:

Field	Type	Method
Id	Number	Number
firstName	String	Person
lastName	String	Person
name	String	Person
email	String	Intenet
phone	String	Phone

Custom Data Generation

The createTestData function will create the above schema.

            NODE_TYPE // javascript
        
async function createTestData(recordCount) {
  const fileName = `customers_${recordCount}.csv`;
  var f = fs.createWriteStream(fileName);
  f.write('id,name,email,phone\n')
  for (let i=0; i<recordCount; i++) {
    const id =  faker.number.int();
    const firstName = getFirstName(i);
    const lastName  = getLastName();
    const phone     = getPhoneNumber();
    const name      = `${firstName} ${lastName}`;
    const email     = getRandomCustomerEmail(firstName, lastName);
    f.write(`${id},${name},${email},${phone}\n`);
  }
  console.log(`Created file ${fileName} containing ${recordCount} records.`);
  f.close();
}

Generate Email

            NODE_TYPE // javascript
        
function getRandomCustomerEmail(fName, lName) {
  const pName = faker.internet.domainName();
  const email = faker.internet.email({ firstName: fName, lastName: lName, provider: pName });
  return email.toLowerCase();
}

Generate First Name

The following function will generate first name. The function takes an integer param, that can be used to set the gender of the name.

            NODE_TYPE // javascript
        
function getFirstName(gender){
  return gender%2==0 ? faker.person.firstName('female') : faker.person.firstName('male');
}

Generate Last Name

The following function will generate a fake last name.

            NODE_TYPE // javascript
        
function getLastName(){
  return faker.person.lastName();
}

Generate Phone Number

The following function will generate a fake phone number

            NODE_TYPE // javascript
        
function getPhoneNumber(){
  return faker.phone.number();
}

Generated Dataset

The information below is an example dataset generated by the code.

            NODE_TYPE // csv
        
id,name,email,phone
1744353443708928,Hattie Shields,[email protected],994-985-4343
7439950444232704,Cornelius Douglas,[email protected],445.834.1232 x04559
3571161470337024,Ella DuBuque,[email protected],(598) 995-8925 x3962
1905977706151936,Andy Auer,[email protected],1-839-408-6820 x7671
7038984255438848,Virginia Rohan,[email protected],254.784.8123 x8950
1184946481790976,Isaac Pagac,[email protected],948-787-4669 x126
437067337170944,Alma Windler,[email protected],(966) 478-7228
4056411071840256,Wilbert Zieme,[email protected],547.786.0668 x195
5202519139549184,Wendy Strosin,[email protected],225-558-2300
4725405374218240,Santos Koch-Bailey,[email protected],973.596.7081 x654

Complete Code

            NODE_TYPE // javascript
        
const fs = require('fs');
const { faker } = require('@faker-js/faker');

// Function: getRandomCustomerEmail
// Param: fName - firstName, lName - lastName
function getRandomCustomerEmail(fName, lName) {
  const pName = faker.internet.domainName();
  const email = faker.internet.email({ firstName: fName, lastName: lName, provider: pName });

  return email.toLowerCase();
}

// Function: getFirstName
// Param: Gender 0 - Female, 1 - Male
function getFirstName(gender){
  return gender%2==0 ? faker.person.firstName('female') : faker.person.firstName('male');
}

// Function: getLastName
// Param: N/A
function getLastName(){
  return faker.person.lastName();
}

// Function: getPhoneNumber
// Param: N/A
function getPhoneNumber(){
  return faker.phone.number();
}

async function createTestData(recordCount) {
  const fileName = `customers_${recordCount}.csv`;
  var f = fs.createWriteStream(fileName);
  f.write('id,name,email,phone\n')
  for (let i=0; i<recordCount; i++) {
    const id        =  faker.number.int();
    const firstName = getFirstName(i);
    const lastName  = getLastName();
    const phone     = getPhoneNumber();
    const name      = `${firstName} ${lastName}`;
    const email     = getRandomCustomerEmail(firstName, lastName);
    f.write(`${id},${name},${email},${phone}\n`);
  }
  console.log(`Created file ${fileName} containing ${recordCount} records.`);
  f.close();
}

recordCount = parseInt(process.argv[2]);
if (process.argv.length != 3 || recordCount < 1 || isNaN(recordCount)) {
  console.error('Include the number of test data records to create. Example:');
  console.error('    node createTestData.js 100');
  process.exit(1);
}

createTestData(recordCount);