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Testing your API with Postman

Published Feb 03, 2017Last updated Feb 24, 2017
Testing your API with Postman

I'm sure you already know the famous tool call Postman. This is a super useful tool for test your API and looks at the response you get from your server. But I see a lot of people just using it as a manual tester. This is not wrong but you can get much better productivity with if you use some of Postman features.

Create your first Simple Test

First thing this is a simple controller in your app where you can fetch a unique post with is ID as params.

/posts/controller.js

import Post from './model';
/**
* GET BY ID
**/
export const fetchPostById = async (req, res) => {
  try {
    res.status(200).json({ post: await Post.findById(req.params.id) });
  } catch (e) {
    res.status(e.status).json({ error: true, message: e.message });
  }
};

/posts/routes.js

import { Router } from 'express';
import * as PostController from './controller';

const routes = new Router();

routes.route('/posts/:id').get(PostController.fetchPostById);

export default routes;

Now time to open Postman. In your left, you gonna see a little folder with a plus sign. If you click there you can now create a collection. Give a little name for your collection. For me, I'm using Postman-Tuto. With that collection, we make our life much easier to test route already create.

Add the route and the GET method in the main area. For me, I add http://localhost:3000/api/v1/posts/588ce463f4741431c918a04b cause I have already created a fake post.

Now when I click send I receive this. Perfect the route is working and the controller + model do their job.

Write your first Postman test

If you click on Test right below the URL container you gonna see this . Now time to write some test. First thing in the right you can see a select menu with test already create by Postman. We can select one already Status code: Code is 200.

If you click send now we can see the test pass 1/1.

Now add the Response body: JSON value check again in your right snippets.

var jsonData = JSON.parse(responseBody);
tests["Post should have title of Title 1"] = jsonData.post.title === "Title 1";

Add this line and now click send.

This is the result.

Add more test

Now an example of a complete test for this routes.

tests["GET By Id Posts - Status code is 200"] = responseCode.code === 200;

var jsonData = JSON.parse(responseBody);

tests["Post should have title of Title 1"] = jsonData.post.title === "Title 1";

tests["Post should have id of 588ce463f4741431c918a04b"] = jsonData.post._id === "588ce463f4741431c918a04b";

tests["Should have no error"] = jsonData.error === false;

Time to save and add new one

Now in the top left, you can see a big Save button. Click on the arrow and save as. Give a name to this route. + you need to add it to your collection.

The runner

In the top left you can see the button Runner if you click it Postman open a new window. Select your collection in the dropdown.

If you click Start Run you can get this.

As you can see I add some new test for show how awesome this tool can be. You can also import your test run and give that to another dev in your team.

Last thing you can also export all your route if you click it in your collection. After the other dev just need to import it and he gets all your route. Now I start to export it in my postman folder inside my server so I can import it if I delete mine on my GUI.

Hope you like this little tutorial and you learn something new today 😃.

P.S You still need to run some test in your controller etc but with the Runner of Postman + the test etc that give you just much more confirmation.


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6Replies
Adam Goldman
6 months ago

Emanuel are there advantages for using postman for testing over nodejs supertest?

Is it easy to integrate postman into travisCI (or another CI service) for conditional deployment?

Emanuel Quimper
6 months ago

I’m using postman only for a + for my test. I still use supertest and ci service, but when I play with the api in postman I just write test in sametime. If you are like me and like having something double check that can maybe be a tool for you. This article was more for showing Postman as a great tool not just an api caller.

Hope you enjoy it. :)

Stephanie
6 months ago

Very interesting post. Thanks for sharing.
But I am wondering how do you test the same request with all the possibilities. Like you test when everything goes well (status 200) and you want to make sure that all the information are properly set. Your example is perfect for that. But now on the same request I want to make sure that if I enter a bad parameter I receive a status 422 or 404. How to you achieve that? Do you duplicate the request and set another set of parameters/tests or is there a configuration that I missed?
Because I would love to have all set, modify my API and the run all the tests through postman and make sure that I didn’t break anything.
Thanks in advance for sharing your thoughts on this.

Emanuel Quimper
6 months ago

Thank Stephanie for the comments :) In the right of postman you have snippets of test. But you can custom them. Like change the status 200 for be >= 400 when you it your endpoint etc. If you look here they have example https://www.getpostman.com/….

Hope that help, if not I can maybe write you a new example and add this to this post :) I want to be sure you get the value of this article :)

Michael Joyner
6 months ago

Emanuel, the above cotroller in .js, is that node.js?

Emanuel Quimper
6 months ago

Yes it’s node.js @Michael Joyner

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