How to Use Postman for API Testing Tutorial 

Postman API testing is designed to help developers build and manage applications with ease. With many companies opting for instant messaging applications, there is an API that receives and sends users’ requests in the background. Thus the need to assess how well those apps are doing is the paramount need for the developers. 

 The enticing bit is that Postman is web-based and totally free, hence its popularity, especially for small businesses. With thorough documentation and many tutorials, developers are finding it an easy tool for testing HTTP calls. 

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 Postman API

 Postman is a stable, lightweight API web testing tool used in building, managing, creating requests, backend testing, publishing, sharing, and documenting APIs. Postman is an API client to help build, visualize data, authenticate, and manage APIs developed in REST, GraphQL, and SOAP.

 Postman automates tests in Continuous Integration (CI) or Continuous Delivery (CD) pipelines, making software development easy and quick. With Postman, developers can code reuse test suites in developing CI/CD pipeline for testing at each singular push.

 Postman API allows developers to design API schema, simulate your API responses, detect bugs and fix errors, and mock public and private servers. It allows developers to produce an API that runs as expected before it is released for consumer use. Performance and response times of APIs can be closely monitored with Postman to allow developers always to know the health of their APIs.

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 Benefits of Postman API

 i. It is free and accessible – All that is required is to get onto their page, create an account, and get started. Since Postman has web and desktop versions, users can easily access the files as long as they have installed the application.

 ii. Saves time – The tests can be scheduled and automated using the Newman or Collection Runner with several iterations, thus saving time, particularly for repetitive tests.

 iii. Multiple Environments and Integration – Postman makes it easy for developers to switch from one mode to another. For instance, it is easy for developers to switch from the JSON to XML environment. Teams can integrate their work as import and export on the platform is made simple, and thus new colleagues do not have to start from scratch. With multiple platform support, developers can use the same collection, reducing redundancy in testing.

 iv. Monitoring is simplified – Developers can track the status codes, response time, and performance of the API.

 v. Free Framework – You do not need to build a framework to obtain responses from the Postman API service.

 vi. User Friendly – This application’s user interface allows the users to easily enter information by filling the headers, selecting HTTP methods, and sending the request.

 Tutorial

 Installation and Configuration

 Postman tool for API testing is open-source and accessible through the web with a chrome extension or desktop application for Mac, Windows, and Linux. However, it is best to use the application version than the web version since the chrome plug-in, in particular, is deprecated and does not contain the latest features that postman has to offer.

 After you have downloaded and run the Postman application, you will be prompted to do a sign-up on opening. Once you have created an account, you select the workspace tools then save your preferences. 

 The Postman Interface

 On the left sidebar, there is History and Collections. Every invoked request is stored in history and can be accessed without having to enter it again. The Collection Tab displays all the requests stored under a particular heading.

 The header has the following:

1.  New. This option allows you to create request, collection, mock server, documentation monitor, and environment.
2.  Import. Allows you to import files on different formats from Collection or Environment
3.  Runner helps in the execution of the test.
4.  Interceptor allows you to incorporate a proxy server.
5.  Sync option synchronizes the API requests on the computer with that in the Postman cloud.
6. The builder section has three major sections Request type, Endpoint Address Bar, and Params. Request type shows the HTTP request sent either GET, POST, PUT or DELETE. The Endpoint Address Bar is where you enter the URL. Params will allow you to enter the parameters needed for the request.
7. The Authorization permits an individual to access the API data while the response section is the dialog box where the responses from the server are displayed.

 Creating a New Request in Postman

 Click on the New option at the header, then select Request and enter a name say “API Project 1” for your request with a short description about it if you wish. Then enter a name for the Collection like “Projects” and save. You shall notice that your collection “Projects” will be populated on the collection folders on the Collection tab with your “Project 1” API in it. Enter the website name or request on the address bar, something like “www.google.com,” and press “Send”. You can also press “Save” should you require to overwrite “Project 1”. 

 Creating a Get Request

 Set the HTTP request to GET from the request list. Then input the request URL ” www.google.com” at the Endpoint Address Bar and click “Send” to execute the request. It then sends the request to the server hosting the Endpoint, and the results will be displayed in the response section.

 Once the execution is complete and all the results are displayed on the response body, then you should check for the various insights from the data results. They include the response text, status code, time taken to complete, and the size of the payload.

 If the status code reads “200 OK,” it means that the response was received successfully and the Endpoint is correct, and the expected outcome returned. A “404 Not Found” status code indicates the unavailability of data with a blank JSON.

 Suppose the time taken to run the URL is high, then it is an indication that the API could be experiencing performance-related problems.

 Creating a Post Request.

 The Post requests are unique since they are designed to create, add, delete, modify, or update data to the endpoint. It is executed in the following way.

1.  Set the HTTP request to POST from the dropdown.
2.  Enter the URL
3.  Switch to the Body tab, then click on Raw and press JSON.
4.  Paste the updated payload script.
5.  Pass the payload.
6.  Check the key header to the Content-Type and set value to application/JSON.
7.  Click “SEND”

 If successful, the status should read “201 Created”. The time taken and the size will also be displayed. Data that has been posted will be shown on the display body.

 Performing a Test on Postman

 Postman tests are performed in two different ways. The first one is a singular test for a particular result; for example, if you want to test the status code, you have to follow the steps below.

 Select GET on the HTTP request dropdown and switch to the Tests tab.

 A snippet panel is automatically populated.

 Select the status code from the snippet section and press “SEND.”

 A test result is displayed showing “PASS Status code is 200”. 

 The PASS is highlighted in a green text box indicating the status code passed the test.

 The second method of testing involves testing different parameters in one go. However, this Postman API testing technique involves some coding to validate responses. Example.

tests["content-type header is present"]=postman.getResponseHeader("content-type");

 tests[Status code is 200"]=responseCode.code==200;

 var jsonData= JSON.parse(responseBody);

 test["Failed test"]=jsonData.cove_color=="Red";

 After running this request, the outcome of the Test Result tab will show.

 PASS content-type header is present

 PASS Status code is 200

 FAIL. Failed test.

 The PASS words are highlighted in green while FAIL in red, indicating tests have been passed or failed, respectively.

Postman vs. RapidAPI Testing

RapidAPI Testing is the preferred API Testing platform among developers. RapidAPI Testing is a cloud-based API testing tool that allows you to create comprehensive API tests (as well as monitor APIs). RapidAPI Testing comes equipped to test all of your REST APIs and offers developers SOAP and GraphQL APIs. RapidAPI testing tool integrates with a user’s internal or external APIs.

The RapidAPI testing dashboard lets users see all the APIs connected to their account. Then, they can jump into the test suite for each API.

RapidAPI Testing is available as an add-on to RapidAPI Enterprise Hub or as a standalone subscription.

• Comprehensive Testing: Create complete and customizable functional API test flows with an easy-to-use interface for visual, automated, or code-based test generation.
• Global Monitoring: Centrally and securely monitor and manage all API tests to ensure the performance of applications, APIs, and microservices.
• Seamless Integration: Improve development efficiency with built-in collaboration capabilities and a dedicated webhook for integration across the CI/CD pipeline.

 Summary

 We can deduce that the Postman tool for API testing is an effective tool in API testing. This API is necessary for information storage, integration with systems that lack a GUI and moving tests to code repositories.

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