Postman Tutorial for API test automation: Create your first automated API test with JavaScript

In this tutorial, you will learn the basics of Postman and how to automate your first API test to check it with JavaScript. This topic is particularly important if test automation is to be integrated into continuous integration processes. You will learn the basics and at the end of the tutorial you will be able to write a request that is checked with JavaScript.

Postman: Platform for API tests, test automation and CI/CD integration

Postman is a powerful API testing and automation platform that enables developers and QA teams to design, test and continuously improve APIs. It was originally developed in San Francisco and now has offices worldwide, including a location in Bengaluru, India. The core of Postman is based on Node.js, making it a flexible and powerful solution for test automation.

Postman offers a wide range of functions:

• API-Repository: A central platform where API tests and artifacts can be stored and shared within teams or partner networks.
• API-Ersteller: Helps design APIs with standards such as OpenAPI, GraphQL and RAML and offers easy integration into CI/CD pipelines.
• Test automation tools: Includes functions for API tests, mock servers, API documentation and test scripting.
• Analysis: Provides advanced features for API monitoring, security alerts and API governance.
• Workspaces: Ideal for teams that work together in public, private or partner workspaces and want to perform API tests in real time.

The Postman documentation and detailed tutorials are available in the Postman Learning Center (PLC) . The tool can can be downloaded and installed here free of charge.

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The Postman user interface (UI) 

Create a workspace for API tests

In Postman, you work with workspaces to organize your API tests. A workspace serves as the central point where you store and manage all test resources. You can create a new workspace using the drop-down menu in the top bar. Here you can specify whether the workspace should be private, public or shared with specific team members.

Step 1: Select template for the workspace

In the first step, you can select a suitable template for your project. The available templates appear clearly in the middle of the screen, with a brief explanation for each template. This helps you to quickly select the best template for the specific requirements of your project.

Step 2: Define workspace names and access rights

In the second step, you give the new workspace a meaningful name and define the corresponding access rights. You can determine whether the workspace is private, public or only accessible to certain team members. This function allows you to precisely control access to sensitive QA data and customize the workspace as required. 

  Notice: Both the name and the access rights of the workspace can be adjusted at any time, provided you have admin rights. This offers maximum flexibility to adapt the workspace to changing project requirements.

                                                          

 Create and use environments: Optimization for flexible API testing 

Environments play a central role in testing APIs, especially in conjunction with variables. They make it possible to use different configurations, for example to send different requests to test and production systems. By using environment variables, dynamic values can be adapted depending on the environment (e.g. test or production environment). 

Create and use global environment variables 

Global environment variables are ideal for frequently used values that are used in various API requests. Examples of global variables are:

• Basis-URLs (e.g   BASE_URL)
• Access tokens, required for multiple API requests 

These variables can also be automatically extracted from an initial authentication request and saved (see point: Script tab). 

Create new environmentNeues Environment erstellen

New environments can be created quickly and easily. Use the plus symbol in the environment administration (yellow box) or the New/Import Buttons (blue Box). Once created, the environments can be selected via the drop-down menu in the top right-hand corner to be used for specific API requests. This enables precise and flexible management of test environments. 

Postman UI for the creation of environments.

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Creation and processing of API requests: Efficient testing and automation of requests 

 

The creation of an API request is a central component of API testing. With a professional QA platform, API requests can be created, customized and tested quickly and easily. There are two simple ways to create a new API request:

Create new API request: 

1. Directly in a collection folder: Right-click on an existing collection folder and add a new request within this collection. 
2. Via the plus symbol in the Workbench: If you have selected a collection folder, you can also create a new API request directly using the plus symbol. 

Postman UI for creating requests

 

 

Edit API request 

If you select an API request that has already been created, a detailed view opens in the Workbench with all the relevant settings and options that you can customize for the request. 

Link: API request - PLC 

 

Postman UI representation of the workbench for processing a single API request

The most important areas are: 

Request type and URL: Select the HTTP method type (e.g. GET, POST, PUT) and enter the target URL of the API. 

• Pro tip: Open the developer tools in your preferred browser (here Chrome), select the Network tab, search for the desired request and left-click on it to select “Copy as cURL”. This can be pasted directly into the text box next to the API type and all parameters are inserted. These can now be exchanged with the variables from the environments. 

Illustration of the workflow for copying a specific cURL from the developer tools of the Chrome browser.

• Params tab: The URL parameters (e.g. ?a=1&b=2&c=3)) that are automatically inserted are displayed here. These can be adapted or extended as required. 

• Authorization tab: Select the appropriate authorization method (e.g. Bearer Token or Basic Auth). The selected method is automatically integrated into the request header. The option to take over the authorization from higher-level requests saves additional time. 

• Header tab: All header parameters of the request are displayed here. Some headers are generated automatically and can be switched on or off using a button to customize the request. 

• Body tab: Define the body of the request, for example for JSON data or login information. Pro tip: Use your browser's developer tools (e.g. Chrome) to copy the cURL request directly and paste it into the text field. All parameters are transferred automatically and can be replaced with environment variables. 

  • • 1	{
      2	"login": "",
      3	"password": "",
      4	"rememberMe": true,
      5	"grant_type": "password",
      6	}

      Example: Use variables such as   and for login data. These variables can be created and used as described in point 4. 

• Scripts tab: In the Script tab, you can add JavaScript commands that are executed either before the request (pre-request scripts) or after the response (post-response scripts). A frequently used example of a post-response script would be the extraction of an access token from the response in JSON format, which can then be saved in the collection and reused for future requests.    

1	pm.collectionVariables.set("token", pm.response.json().access_token)

The complete documentation offers numerous additional scripting options to automate and optimize the API test process. Scripts - PLC. 

 

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Your first API test: Automate quickly and easily with JavaScript 

With just a few steps, you can create and run your first API test - all using JavaScript. In this final section, we'll show you how to create an API request, connect it to an environment variable and test it automatically. 

Create a new environment and save any variable 

New environment with variable 

1. Create a new environment: Click on “Create environment” and save any environment variable. 
2. Do not forget to save: Cmd + S (Mac) or. Ctrl + S (Windows) to save the changes.
3. Select environment: Make sure that you select the new environment in the top right-hand corner as the active environment so that it is used for the request. 
   
   

Create a collection with your API test 

1. Name collection and test:  Give your collection and the test meaningful names so that you and your team can quickly recognize which test it is. 
2. Select HTTP method: Select the HTTP method „GET“.
3. Insert RL: Copy the following URL into the input bar  https://postman-echo.com/get?myQueryParameter=
   This URL will return the transferred data as a response. In this case, the query parameter   myQueryParameter with the value of the environment variable  myEnvironmentVar. 
4. Use environment variable: Make sure that the spelling of the variables is exactly the same in both the environment and the query. This is indicated by the curly brackets  . 
   
   

Create a script for automated testing 

1. Switch to the “Scripts” tab: Go to the Post-response tab in the Workbench. 
2. Paste code: Copy and paste the following JavaScript code: 

This code reads out the response to the request and checks whether the value of the query parameter matches the value of the transferred environment variable. 

Check the result:

You have now successfully performed your first API-Test . After you click on Send, the request is executed and the response is automatically checked against your test script. 

• View response: After the test has been executed, you can view the complete response in the Body tab. You will notice that the value of the myQueryParameter in the response matches the value of myEnvironmentVar . 
• Test confirmation: You can view the results of your test in the Test Results tab. This confirms that the variable has been transferred correctly.
  
  

 Conclusion & outlook: Postman for efficient API testing and automation