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By Kimserey Lam with

Using Newman In Nodejs

May 29th, 2020 - written by Kimserey with .

Few weeks ago we looked into automating Postman collection run using Newman CLI. On top of using the CLI directly, Newman can also be used in a NodeJS application which makes it very versatile to create tools for testing. Today we will look at how we can use Newman as a NPM library and see the options provided.

Newman Library

Let’s start by exporting a sample collection in JSON format:

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{
	"info": {
		"_postman_id": "32a14dcc-18e2-4a9b-8614-58061829c75a",
		"name": "Test  Collection",
		"schema": "https://schema.getpostman.com/json/collection/v2.1.0/collection.json"
	},
	"item": [
		{
			"name": "GET petshop",
			"request": {
				"method": "GET",
				"header": [],
				"url": {
					"raw": "http://localhost:5000/pets",
					"protocol": "http",
					"host": [
						"localhost"
					],
					"port": "5000",
					"path": [
						"pets"
					]
				}
			},
			"response": []
		}
	],
	"protocolProfileBehavior": {}
}

Then we can install Newman via NPM:

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npm install newman --save

Next we can simply use it by calling the #.run(...) function which runs the collection.

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const newman = require('newman');

newman.run({
    collection: require('./sample-collection.json'),
    reporters: 'cli'
}, function (err) {
	if (err) { throw err; }
    console.log('collection run complete!');
});

#.run takes an option object which allows us to set different option that we would normally provide as CLI options. Here we set collection which is the JSON collection and reporters which is the summary reporter format which will be printed once the collection has completed its run.

The two other important parameter of the option is the environment, it can either be defined as an object or a string path pointing to an environment varaible file exported through Postman.

For example we export the following environment:

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{
	"id": "85f1bf17-34ac-42af-a8bd-531ef44a19fb",
	"name": "Example Env",
	"values": [
		{
			"key": "HOST",
			"value": "localhost",
			"enabled": true
		}
	],
	"_postman_variable_scope": "environment",
	"_postman_exported_at": "2020-04-06T08:47:05.528Z",
	"_postman_exported_using": "Postman/7.21.2"
}

And modify our collection to use the environment:

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{
	"info": {
		"_postman_id": "32a14dcc-18e2-4a9b-8614-58061829c75a",
		"name": "Test  Collection",
		"schema": "https://schema.getpostman.com/json/collection/v2.1.0/collection.json"
	},
	"item": [
		{
			"name": "GET petshop",
			"request": {
				"method": "GET",
				"header": [],
				"url": {
					"raw": "http://{{HOST}}:5000/pets",
					"protocol": "http",
					"host": [
						"{{HOST}}"
					],
					"port": "5000",
					"path": [
						"pets"
					]
				}
			},
			"response": []
		}
	],
	"protocolProfileBehavior": {}
}

And we can now provide the path to our exported environment:

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const newman = require('newman');

newman.run({
    collection: require('./sample-collection.json'),
    environment: './env.json',
    reporters: 'cli'
}, function (err) {
	if (err) { throw err; }
    console.log('collection run complete!');
});

The second argument of #.run is a callback returning an error which would occur if Newman failed to run the collection due to some unexpected error - only fatal errors unrelated to request or test failing - and a summary with the result of the collection.

Events

So far we only did what we the CLI allowed us to do. But the advantage of running in a Node application is that we can ho9ok onto Newman events to build logic around it.

For example, we can hook onto start to add some logic before the collection starts:

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const newman = require('newman');

var token = "";

newman.run({
    collection: require('./s.json'),
    environment: './env.json',
    reporters: 'cli'
}, function (err) {
	if (err) { throw err; }
    console.log('collection run complete!');
})
.on('start', function (err, args) {
    token = retrieveToken();
})
.on('beforeRequest', function (err, args) {
    args.request.headers.add({key: "authorization", value: token });
});

function retrieveToken() {
    return "abc";
}

For example here we hook the start of the collection with a function getting an authorization token and use beforeRequest to add an authorization header to each of the requests.

Another interesting event is request which gets triggered after each request complete and extract the results to be displayed once the whole run is over.

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const newman = require('newman');

var token = "";
var results = [];

newman.run({
    collection: require('./s.json'),
    environment: './env.json',
    reporters: 'cli'
}, function (err) {
	if (err) { throw err; }
    console.log('collection run complete!');
})
.on('start', function (err, args) {
    token = retrieveToken();
})
.on('beforeRequest', function (err, args) {
    args.request.headers.add({key: "authorization", value: token });
})
.on('request', function (err, args) {
    const res = JSON.parse(args.response.stream.toString());
    results.append(res);
})
.on('done', function (err, args) {
    console.log(results);
});

function retrieveToken() {
    return "abc";
}

In this example we expect the result of the requests to be a JSON format so we can use JSON.parse(args.response.stream.toString()) to extract the JSON result from the response. And that concludes today’s post!

Conclusion

Today we looked at how we could use Newman as a NPM package library. We started by looking at how we could install it and run a collection. Then we moved on to look into how we could subscribe to events emitted by Newman to add custom logic with an example of authorization implementation and results aggregation. Using Newman as a library opens a lot of possibilities to script tools in JavaScript. One example would be to aggregate the results and build a custom HTML report using the results. I hope you liked this post and I see you on the next one!

External Sources

Designed, built and maintained by Kimserey Lam.