Ranger: A test data generator

Ranger is a test data generator that lets you create customized, correlated test data using the Ranger language.

This example Ranger file

produces such an output

{"age":37,"sex":"female","name":"Lucy","id":"Lucy123","pin":"1683","eyes":"brown"}
{"age":57,"sex":"male","name":"Robert","id":"Robert123","pin":"4242","eyes":"brown"}
{"age":42,"sex":"female","name":"Lisa","id":"Lisa123","pin":"2016","eyes":"brown"}
{"age":60,"sex":"female","name":"Emily","id":"Emily123","pin":"8119","eyes":"brown"}
{"age":50,"sex":"male","name":"Max","id":"Max123","pin":"4061","eyes":"brown"}
{"age":54,"sex":"male","name":"Robert","id":"Robert123","pin":"5378","eyes":"brown"}
{"age":52,"sex":"female","name":"Emily","id":"Emily123","pin":"4765","eyes":"brown"}
{"age":38,"sex":"male","name":"Robert","id":"Robert123","pin":"8901","eyes":"brown"}
{"age":39,"sex":"female","name":"Emily","id":"Emily123","pin":"6529","eyes":"blue"}
{"age":28,"sex":"male","name":"Max","id":"Max123","pin":"6623","eyes":"brown"}

Find more examples here.

How does it work?

You design test entities in a .ranger file.

Then, there are two ways to generate data:

• Use the ranger command line tool to create CSV or JSONL files.
• Use the Node.js library to generate JavaScript objects and use them in your code.

Get editing assistance via the Visual Studio Code Extension.

Command Line Interface

To setup the ranger command line tool, you have two options.

Option 1: Download binary

Download one of the prebuilt binaries (Windows and Linux x86 only).

Option 2: Install via npm

Install Node.js.

Open a terminal and execute

npm install -g ranger-lang

Test it

Create test file Customer.ranger.

Open a terminal and execute

ranger Customer.ranger -c 100000 -f jsonl

It will generate 100'000 rows and save the output to file generated/Customer.jsonl.

Node.js Library

Setup

Open a terminal inside the Node.js project folder and execute

npm install ranger-lang

In order to follow the examples below, create the test file Customer.ranger.

ObjectGenerator API

Create an ObjectGenerator, call next() to retrieve the next generated object.

import { createObjectGenerator } from 'ranger-lang';

const generator = await createObjectGenerator({ filePath: './Customer.ranger' });

for (let i = 1; i <= 1000; i++) {
    console.log(generator.next());
}

Node.js Streams API

Create a Readable Node.js Stream and pipe it to a Writable Stream.

import { createObjectStream } from 'ranger-lang';
import stream from 'stream';

const source = await createObjectStream({ filePath: './Customer.ranger' }, 1000);   // yields 1000 elements

const sink = new stream.Writable({
    objectMode: true,
    write(chunk, _encoding, callback) {
        console.log(chunk);
        callback();
    },
});

stream.pipeline(source, sink, (error) => console.log(error || 'Success!'));

Test file

Create a new file Customer.ranger and paste the following content into it:

Entity Customer {
    age: random(20..60)
    sex: random("male", "female")
    name: map(sex => [
        random("James", "Robert", "Max"),
        random("Emily", "Lucy", "Lisa"),
    ])
    id: f"{name}123"
    pin: /\d{4}/
    eyes: weighted("brown":80, "blue":20)
}