RestAssured Framework Simplified: Ultimate Guide for API Testing in 2024


Java based RestAssured Framework

Automation Testing is one of the essential aspects for organizations that build sophisticated applications. RestAsssured Framework, a Java-based framework, is commonly used for REST API Automation Testing in many companies. The framework enables users to access functionality and identify issues in REST Web Services. However, API Testing is not straightforward, especially in Java. But, the complications involved in API Testing can be eliminated as the RestAssured framework simplifies requesting and comprehending complex tests. 

Upon a complete walkthrough of this article, you will gain a decent understanding of API Testing and RestAssured Framework along with the salient features that they offer. You will also learn about the steps required to perform API Testing using the RestAssured Framework.

Table of Contents


  • Understanding of API Integration.
  • An idea of Software Testing.

Introduction to APIs

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API or Application Programming Interface is a type of software interface that connects different software with minimal coding. Most organizations use APIs as it acts as a bridge between services and products to interact with one another with minimal hassle. In other words, an API acts as an intermediary that transfers data among systems. Generally, API requests are processed from client applications to web servers to authenticate and retrieve information. 

Without using APIs, companies might lack connectivity and information that will compromise their performance and hinder productivity. APIs provide flexibility to connect with new business partners and access new markets, which can be helpful in generating returns and implementing digital transformation. Companies like PayPal, Google Maps services, and Twitter rely on APIs to assist other organizations or developers in creating advanced applications while still maintaining security and control over the information they share. As APIs provide high security by using Tokens, Signatures, and Transport Layer Security (TLS) Encryption, organizations can work hassle-free without exposing their sensitive information.

Introduction to API Testing

API Testing
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API Testing involves assessing the Functionality, Performance, Security, and reliability of sophisticated applications. Since there is an absence of Graphical User Interface (GUI), API Testing is carried out at the message layer, where the validation of application logic is effective. API Testing plays a vital role in building robust applications as it helps in Removing Bugs, Validating Logic, Determining Vulnerabilities, and more. Often Agile and DevOps teams prefer API Testing over UI automation testing because it expedites the testing workflows; what would take a few hours in GUI testing can be performed in a few minutes with API Testing.

Usually, applications have three separate layers that include a User Interface layer or Presentation layer, an Application User Interface layer for processing business logic, and a database layer where the data can be manipulated. API Testing is carried out at the business process logic, a crucial step where all the interactions between database and user interface take place.

Need for API Testing

Need for API Testing
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Testing has three different layers that are often depicted using the test pyramid, a term coined by Mike Cohn, author of “Succeeding with Agile.” It consists of three layers that represent the types of testing involved and implies the amount of testing required at each layer. 

Looking at the test pyramid, it can be observed that the first layer, i.e., unit/component test layer covers 70% of the code. The second layer — API or service tests layer — aims to focus on business rules of applications under test and covers 20% of the code. Testing the second layer is to ensure whether all the implemented functions are working accurately. The final layer or the workflow test part is performed by UI, which is responsible for ensuring the accuracy of its built features. Since UI testing often changes due to the ever-changing needs of presenting information, it is prone to changes. As a result, testing professionals focus less on this section.

Advantages of API Testing

A few of the advantages of API Testing are mentioned below:

  • Data is exchanged in API Testing through XML and JSON, where XML and JSON are known to have Structured/Semi-Structured data. As XML and JSON can accept any programming language, automating the tests becomes easy.
  • As API Testing is achieved at a faster rate, the feedback retrieved will be quicker. This will enhance the overall productivity of the business. API testing is done before GUI (Graphical User Interface) testing, due to which fixing minute errors while enhancing the core functionalities is effortless.
  • API Testing allows the implementation of automated tests with high coverage as they have specifications that include functional and non-functional testing.
  • API Testing can be performed even before the complete application is ready with the user interface, thereby expediting the release of solutions in the market. 
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Understanding Java RestAssured Framework

RestAssured Framework is an Open-source Java-based framework used by programmers and developers for testing and validating REST services. Built from the ground up to cater to the varying needs of testing, RestAssured Framework provides a Domain-Specific Language (DSL) to create and write powerful tests for RESTful APIs efficiently.

The RestAssured framework also supports Behavior Driven Development (BDD) or Gherkin style of writing for enhanced readability and clean coding to enable seamless testing workflows. To simplify the testing tasks, REST Assured aids in easy integration of classic testing frameworks such as TestNG and JUnit runner that are used by organizations to assess their REST web services. 

Key Features of RestAssured Framework

Features of RestAssured Framework
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With RestAssured Framework, Automation Testing professionals can create customized and user-friendly HTTP requests that can be used to test RESTful Web Services. This helps in testing a variety of request combinations with respect to the business logic layer of applications. Fetching data is easy, regardless of the complexity of JSON structures, because REST Assured simplifies the validation process for users with human-readable results.

The main features of RestAssured Framework that enable it to be more resourceful follows:

  • It eliminates the aspect of writing complex codes that are required to set up an HTTP connection, send or receive a request, and parse a response. 
  • It makes the test results easy to read as it supports notations such as ‘given’ or ‘then’ or ‘when.’
  • Integrating REST Assured into a continuous delivery setup is easy when paired with Java testing frameworks like TestNG, JUnit, etc.
  • Apart from technical response data validation, REST Assured also supports data-driven API testing to allow testers to perform complex tests.  
  • REST Assured serves as the main support system for XML- and JSON-path syntax for checking several elements of the response data.

API Testing with RestAssured Framework

API Testing
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RestAssured Framework helps assess and identify errors found during the process of application development. In order to use RestAssured Framework for API Automation Testing, knowledge of suitable IDE (IntelliJ or Eclipse), Maven, frameworks such as TestNG, or JUnit is necessary. The two ways used for testing Rest APIs are Manual Testing and Automation Testing. The most commonly used method is Automation testing for REST APIs as it helps interpret results effectively.

Rest API uses five HTTP methods for requesting commands as listed below:

  • GET: Retrieves information from a specific URL.
  • PUT: Updates previous resources or creates new information at the specified URL.
  • PATCH: Partial updates.
  • POST: Develops a new entity and is also used to send information to the server for uploading files or information.
  • DELETE: Deletes the present representation at a particular URL. 

RestAssured Framework uses Java and Maven, an automation tool based on POM (Project Object Model) primarily used for Java projects that provides developers with a total lifecycle framework. 

Steps to Test GET Command

A GET command request can be tested using the following steps:

  • Open Eclipse.
  • Create a ‘Java package’ and ‘Java Class’ and name them, respectively.
  • Write the code as mentioned below:
Testing Get Command
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  • Choose ‘Run As’ and then click on ‘TestNG’.
  • The output is obtained as shown below:
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As seen in the above code, the status code is 200 which means it has passed the test. Similarly, other HTTP methods can be used to perform API testing using the RestAssured Framework. 

For further references and examples of REST Assured, you can access the GitHub repository of REST Assured.


Since API Testing is a critical part of any development life cycle, REST Assured Framework is one of the most widely used Web Services Testing tools in Java. Advanced features, along with simplicity in implementation, make it a must for any testers to ensure quality in the end product. Master the Rest Assured framework for effective API testing, ensuring robust and reliable automation.

This blog introduced you to API Testing and its advantages. It further highlighted the steps required to perform API Testing with RestAssured Framework. If you want to integrate data from various data sources into your desired Database/destination for free and seamlessly visualize it in a BI tool of your choice, Hevo Data is the right choice for you! It will help simplify the ETL and management process of both the data sources and destinations.

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Share your experience of learning about Java RestAssured Framework. Let us know in the comments section below!

Freelance Technical Content Writer, Hevo Data

Srividya loves to combine her flair for writing and problem solving ability to help businesses with in-depth articles on data integration and analysis. She has provided detailed content to support individuals exploring these complex subjects.

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