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API Testing- Postman Vs Rest Assured

Introduction :

The goal of innovation and modernization has shifted from simple market differentiation to a

more ethical pursuit of betterment for society as a whole. New demands have been placed on

server-side software as a result of the ongoing digital disruption and innovative mobile

technologies. As a result, server-side programmed must now accommodate laptop,

smartphone, and hardware platforms (like IoT (Internet of Things). APIs serve as catalysts

for digital transformation by allowing organizations to safely modernize their legacy systems.

APIs should be fine-tuned to meet the unique needs of each business scenario. Successful

APIs are the result of rigorous API testing.  In this blog, we'll talk about two methods for

testing APIs: REST Assured and the Postman tool.

What is API ??

To accomplish complicated integration services, the APIs used to consume the enterprise

application and many functionalities must communicate with core functionality, databases, and

other services that may store data in a wide variety of forms (XML, JSON, etc.) With APIs,

businesses can generate more money by making their most valuable resources available to a

wider audience. The purpose of an API gateway is to provide a single point of access to a

collection of APIs. The use of an API gateway allows for the provision of the most suitable

API to each client, the minimization of number of requests made by each client, and the

enforcement of suitable security and control mechanisms.

What is API Testing??

Application programming interface (API) testing is a subset of software testing that involves

verifying the expected functionality, stability, performance, and security of an API or

collection of APIs through both standalone tests and also as element of such an integration

test. It has several important benefits, including better coverage during the testing cycle,

reduced resource usage, and faster, more reliable implementations. While evaluating

software, API tests push them to their limits with unusual data and configurations. In-house

or an offshore QA team can benefit from API testing depending on the project duration,

integration needs, and desired functionality.

What is Postman Tool??

Postman is an automatic and interactive tool for prototyping APIs, and it also includes

outstanding testing capabilities. To test an API, a request is sent to a web server and the result

is analyzed. It provides a user-friendly interface for making requests and viewing responses.

It has helpful capabilities for persisting data and modelling how a user would be engaging

with the system, and it can be used automatically and in a wide range of contexts for

repeatable, reliable testing.

Why is Postman Tool preferable??

Postman, formerly known as a validation browser plugin, is now the favorited tool for QA

experts when it comes to developing, testing, and managing APIs. Abhinav Asthana created

Postman as a side project to streamline the application programming interface (API)

workflow during software development and testing. More than 4 million people throughout

the world are currently making use of the tool.

Postman is cross-platform and may be used on Linux, Mac OS, and Windows, It provides

additional flexibility for API design. Postman is a tool that facilitates the creation of tests for

API calls by functional testers, eliminating the need for lengthy and laborious scripting. Some

benefits of Postman include:

  • User-friendliness

The intuitive UI makes it easy for testers to generate test suites by populating pre-made

forms. Postman code snippets give validation examples including response code, response

time, and more, facilitating the development of scripts.

  • Ease of access

With the Postman app or browser extension, users may quickly and easily access their files

from any device with an active Postman account.

  • Diverse Capabilities

Postman allows you to change the environment in which APIs are developed, as well as save

your progress, convert APIs to code, and convert between the two in real time.

  • Powers to monitor requests

Postman provides a number of status codes for checking HTTP responses. Such examples

include a request being granted access, a request being denied access, a response being

empty, and a request being deemed invalid.

These advanced capabilities streamline every step of creating and distributing APIs for

programmers. However, Postman has significant drawbacks when it comes to testing APIs,

especially automation testing.

  • Confined testing space

Postman shines when testing a RESTful API, but falls short when working with other types

of APIs (like SOAP).

  • Little potential for script reuse

Users of Postman cannot modify or contribute to existing scripts. This necessitates that testers

constantly devise fresh test scripts for each project.

  • Restrictions on Integration

The Agile process is made possible by APIs, but the technology itself offers limited support

for integration. Problems arise while trying to integrate Postman with preexisting

infrastructure and promote teamwork.

For manual testing of APIs, especially REST APIs, Postman comes highly recommended in

this retro context. Instead of using Postman to do complex API tests, QA teams might benefit

in various ways from using a dedicated API testing automation platform. The use of

organized test suites and frameworks is one such advantage. The time and effort required to

find and organize test cases is reduced for users. Postman design ends up being a barrier to

cross-departmental cooperation in Agile teams because constant contact between all members

is essential.

API Platform – Postman :

What is Rest Assured??

Testing RESTful Web Services is made easier using Rest-Assured, a Java library. This library functions as a "headless Client" to reach RESTful APIs. It is widely used for testing both JSON and XML-based web apps. As an added bonus, it works with every particular method, covering GET, PUT, POST, PATCH, and DELETE. TestNG, Maven, Java, and an Integrated Development Environment (IDE) are prerequisites (IntelliJ, Eclipse, etc.) The four fundamental HTTP operations are GET, PUT, POST, and DELETE. The following CRUD actions correspond to these queries:

  • Using GET, you can get a representation of a resource from a certain URI. No lingering server response is expected after a GET.

  • By using a URI as its target, PUT can modify that resource. If the server lets users create their own URIs, PUT is another way to invent a fresh resource at that location.

  • New resources can be made with POST. As part of the response message, the server includes the newly allotted URL for the object.

  • In order to remove a resource from its specified URL, DELETE is needed.

Creating HTTP requests for the Restful server is as flexible as it is fun. This lets us put the core business logic through its paces by simulating a wide variety of scenarios, all with the same set of Requests.

The Rest-Assured library also provides the capability of validating server-sent HTTP responses. For example, we may analyze the response's Headers, Status message, body, and Status code. Due to its flexibility, Rest-Assured can be utilized as a testing library.

Why is Rest Assured preferable??

For the purpose of creating robust and easily maintained tests for RESTful APIs, REST Assured offers a domain-specific language (DSL). Most companies' API test automation utilizes REST assured, making it one of the most popular libraries. Rest assured also has the ability to verify that a server's HTTP response is correct. In terms of testing, Rest-Assured is a highly flexible library. Based on the available data, we have confidence in the dependability of REST Assured Java library. We require REST Assured for the following main reasons:

  • Being an open-source library including an active development community makes it a tempting choice for API automation.

  • In the past, testing APIs required the use of dynamic languages such Ruby and Groovy, which presented significant difficulties.

  • Java makes testing and validating REST services more difficult. REST Assured makes everything easier and more streamlined. With the help of this module, delivering encrypted HTTPS requests only requires the Java Code with few lines a few lines of the Java code.

  • After the basics like integration testing and API are mastered, reasonable confidence may be gained by automating the backend with rest assured. This means we can devote more resources to front-end testing.

Postman Vs Rest Assured - API Testing :

Major dissimilarities - Postman and Rest Assured:

  • Reusability of Code

Because the Rest Assured client is written in Java, it's simple to modify existing methods for usage in different tests. In contrast, Postman does not offer a way to recycle old scripts. When deciding among Postman and Rest Assured, it's best to go with the latter if you're working on a sizable project or plan to scale the testing as in future.

  • Functional Simplicity

The actual programmed is called Postman, and the library is called Rest assured. It's easy to get started with Postman because of its intuitive UI and the fact that it can be used directly from a web browser. The use of an integrated development environment (IDE) is also not required.

While Rest Assured's Then/When/Given test specifications make the tests simple and easy to understand by anyone, Postman's absence of a graphical user interface makes it more accessible.

  • Complete System Evaluation

Consider a scenario where you need to ensure that the data you retrieved from the internet has been processed properly by API and saved to the database. Using Rest Assured is the superior option for end-to-end testing scenarios. As a framework, Rest Assured makes it easy to incorporate additional CI/CD tools, such as Jenkins. Thus, we may readily protect it with the aid of dependencies. In contrast, Postman provides weaker backing for such amalgamation.

Postman's excellent user interface makes it a viable choice even if you're primarily interested in debugging or performing manual exploratory testing. Notwithstanding Postman's ability to automate tasks, this comparison between it and Rest Assured hinges mostly on the extent to which the two may be used together.


There are many advantages to using Postman, but here are a few:

By making HTTP requests to a web server and reading the response, Postman is useful for testing application programming interfaces. The following are just a few of the many reasons why this is becoming standard practise in the most prestigious software testing firms:

  • The usage of the Postman tool does not necessitate the purchase of a license.

  • After signing into your Postman account, you may quickly and easily have access to this user-friendly tool.

  • With Postman, you can easily transfer and exchange test cases between different environments and platforms. As this is the case, working with and managing test cases is a breeze.

  • Build test suites quickly and easily. Postman enables the generation of test suites in addition to groupings of system testing activities.

  • Iterative test runs can be conducted with Postman with either the Newman or Collection Runner tools.

  • Postman's collection feature makes it simple to keep your tests up to date.

  • With Postman, you can try out various API formats including GraphQL, SOAP, and REST, SOAP, and GraphQL with minimal setup.

  • The Postman tool could be incorporated into the continuous integration and continuous delivery pipeline.

  • It's simple to include into existing workflows and programmed like Jenkins.

  • By using global variables, it is possible to save information from previously run tests. While making API calls between two APIs, these variables can be passed back and forth like environment variables.

  • With everything safely stored in the cloud, information may be accessed whenever it's needed. Many test cases include interdependencies; for example, one test case may need data from another test case, in which case postman would need to retain that data.

Several disadvantages of utilizing Postman are as follows:

  • Overloading Postman with too many API calls will cause it to crash.

  • Keeping track of all the donations and requests in a huge undertaking can be a challenge.

  • With the potential for substantial repetition of code when dealing with dynamic API requests that Postman facilitates, it is not the best API tool for managing a workspace programmatically.

There are many advantages to using Rest Assured, but here are a few:

  • It's open-source, which means you can use it without paying anything.

  • When compared to Apache Http Client, it has a lower minimum amount of code required.

  • Prior to reaching a destination, its initial setup generally simple and uncomplicated.

  • The JSON and XML formats for responses are easily parsed and checked for validity.

  • Code is more legible and tidy due to the BDD (Behavioral Data-Driven) methodology it employs, as well as to the use of keywords such as then(), when(), given(). Version 2.0 introduces this function.

  • High quality syntax.

  • Extremely abundant with pre-made claims

  • An immediate declaration of the response status and time.

  • On-the-fly checking of headers, cookies, Content-Type, and other headers is possible.

  • Superior mechanism for recording events.

  • The REST Assured framework allows for the scalability and reuse of code.

  • Compatible with a wide variety of different Java libraries, including the TestNG and Junit test frameworks and the Extent and Allure reporting frameworks.

  • Superior assistance for a wide variety of API authentication methods.

  • May be used in tandem with Selenium-Java to fully automate the software development life cycle.

  • Provides support for Json Path and XmlPath, which facilitates the processing of JSON and XML responses. Both are automatically incorporated into Rest Assured.

  • The JSON Model Validation library can be utilised to ensure the integrity of a JSON schema.

  • Includes checking against an XML schema

  • When combined with CICD (Continuous Integration and Continuous Delivery) and Maven, Rest Assured becomes even more powerful.

  • This release marks the availability of REST Assured 4.1.2. New functionality includes compatibility with Java 13.

  • Allows for the submission of information in many areas

  • Has compatibility with Kotlin, Scala, Spring Web Test Client, Spring Mock Mvc.

Several disadvantages of utilizing Rest Assured are as follows:

  • It does not have direct support for testing Simple Object Access Protocol (SOAP) application programming interfaces.

  • Good familiarity with Java programming is a prerequisite for using this package.

  • Moreover, Rest Assured lacks any sort of built-in reporting capabilities.

  • REST Assured does not guarantee thread safety.

Conclusion :

Choosing the best API testing tool is complicated by a wide range of criteria, thus there is no simple this-or-that answer. Our comparison of Postman and Rest Assured should have made it easier for you to evaluate the benefits of each programmed. Over the years of providing API testing assistance to a broad variety of clients around the world, we have made employing both the Postman and Rest Assured. For the same reasons, we chose Postman over Rest Assured and advise you to accomplish the same.

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