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(Micro) Service Testing with Postman - Newman - Docker

Postman seems to become a defacto tool for service testing because the Postman is very user-friendly, easy-to-learn, all-in-one, lightweight and collaborating tool. Postman has been used for a long time but recently it has growing popularity because of a stable native application, collaboration feature after version 6.2, sharing of collections for team, interactive working with the team, mocks for isolated testing, environments for running the test for different test environments such as local, development, stage ... and many more features. For me, one of the biggest features is easy-to-use for everyone in a team so everyone in a team can use and update a postman collection easily. In this post, I want to explain how postman can be used efficiently.

Testing a Service and Writing Tests

With postman testing service is simple. Postman supports many methods like POST, GET, PUT, PATCH. Just select the correct method and hit the service URL you want to test. Postman also has everything that you need for complex requests headers, body, and parameters list. If you need something to prepare before sending the test request you can do it in the 'Pre-request Script'. If you need authorization you can add it 'Authorization' part which is an alternative to adding 'Authorization' parameter in the 'Header' section. If you want to check the not only the status code but also returning data you can add some assertions in the 'Tests' section. Postman supports Chai Assertion Library as BDD you can add self-descriptive assertion functions to your tests.

For complex scenario, you can write some javascript in the tab to simulate real behavior of your users. In the following scenario, a basic payment process is started with a post request and then the status of the request becomes `processing` but after that client needs to check the backend for each second until the status of the process become `completed`. For this scenario, in the `payment/payment-processing` request, until the status of this request is `processing` it calls itself recursively. If the status is not `processing` then it calls the next requests with another great feature of postman `setNextRequest` as  `postman.setNextRequest("payment/payment-complete")` see the example:

Pre-Request Script For Creating Data Dynamically

The pre-request script is designed to run something before the test so we can use it creating/updating/deleting test data for comprehensive test cases. In this section, you can use the embed node packages like `atob` and `btoa` for base encryption or `cheerio` is a form JQuery library to get value from a web object or `CriptoJs` cryptographic library to encrypt data with AES, DES or SHA. You can check the full list of embed libraries from postman document.

In the following example, for RSA encryption with base64, I use an external web application. In the pre-requests tab of the request, `myData` is encrypted by sending a request to this web application. This is another important feature of the postman.

Running Postman Tests With Postman

You can run a collection with Postman collection runner easily by setting environment if necessary. Firs you can get my test collection which is written against to the blog project on GitHub. You can check the `service-test` section since it is a full project including every test that you need in your CI/CD. To run the tests, just click the play button next to the collection name, it opens the run panel then you click the `Run` button. See the following images:

Running Postman Tests With Newman

Newman is the CLI companion of postman so that you can run your tests with your environment by CLI. This is developed for integrating your test to CI/CD environment easily. In this example test data is created before the test run for a comprehensive test result. The full command is as follows:

You need node first, check this, then install the required packages, newman and newman-report-html:

npm install -g newman
npm install -g newman-reporter-html

to run with collection json:
newman run blog-sample-service.postman_collection.json \
 -e blog-local.postman_environment.json \
 --reporters cli,html \
 --reporter-html-template report-template.hbs

to run with collection url:
newman run \
 -e blog-local.postman_environment.json \
 --reporters cli,html \
 --reporter-html-template report-template.hbs

Running Postman Tests With Newman in Docker

For a better approach to run test on CI/CD pipeline is to use Docker so that we will not need to install any test related tools/languages/technologies to the client machine. This is becoming one of the industry standards. 

Check the Dockerfile in the project. Basically, the base image is node installed Debian, we are installing the required node package which is newman and newman-reporter-html. Then we are running the test inside newman folder and the report will be created inside /newman folder. This Dockerfile gives us a newman entry point which can run it with newman commands. I have create Newman image in hub.docker, so we need to pull it first then we use it.
docker run \
 --network host \
 -v $PWD:/newman \
 gunesmes/newman-postman-html-report run  \
 -e blog-local.postman_environment.json \
 --reporters cli,html \
 --reporter-html-template report-template.hbs

We need to restore data during the test some data need to be ready. For each run, the database should be restored with the script provided in restore_database.sql. This file can be run by

Get the  Postman Collection and the project.

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