Hand-on Guide to API Testing with Karate

Aravind Subbarao

Introduction: Test automation has become an integral part of software development processes, aiding in efficient and reliable testing. Selenium has long been the go-to tool for web automation testing, but in recent years, a new contender has emerged: Karate.

One key reason I am writing about Karate vs Selenium is the parallel it has to the David vs Goliath story! I remember this quote from Transformers as I write this article

“At the heart of every legend, there is truth: a few brave souls unite to save the world. We can be heroes in our own lives, every one of us, if we only have the courage to try.”

— Optimus Prime, Transformers: The Last Knight

Karate is an open-source framework that offers unique advantages over Selenium. In this article, we will compare Selenium to Karate and present five compelling reasons to make a switch.

  1. Simplicity and Productivity: Karate simplifies the process of test automation by offering a more intuitive and readable syntax. It employs a Behavior-Driven Development (BDD) like approach, where tests are written in plain English, making them more accessible to non-technical stakeholders/users. Additionally, Karate combines test data, assertions, and HTTP calls into a single test script, reducing code duplication and improving productivity.
  2. Native API Testing: While Selenium primarily focuses on web automation, Karate goes beyond that. It is a versatile tool that supports API testing out of the box. With Karate, you can seamlessly switch between web and API testing within the same framework, eliminating the need for additional tools or libraries. This native API testing capability allows for comprehensive end-to-end testing, providing a holistic approach to test automation.
  3. Built-in Test Reports and Debugging: Karate offers built-in HTML reports that are generated automatically after each test run. These reports provide detailed information about test results, including assertions, request and response details, and error messages. This feature aids in effective debugging and troubleshooting, allowing testers and developers to quickly identify and rectify issues. Selenium, on the other hand, requires additional plugins or libraries to generate comprehensive test reports.
  4. Data-Driven Testing Made Easy: Data-driven testing is a crucial aspect of automation testing, enabling the execution of tests with multiple datasets. Karate simplifies data-driven testing by allowing data tables to be embedded directly in test scripts. This eliminates the need for external data files or complex code, making it easier to manage and maintain test data. Selenium requires additional frameworks or libraries to achieve the same functionality.
  5. Integrated Test Doubles: Karate’s integrated test doubles feature provides a convenient way to simulate backend services or dependencies. It allows you to create virtual servers that respond to API requests made by the application being tested. This capability is particularly useful in scenarios where the actual backend services are unavailable or not yet developed. Selenium lacks built-in support for creating test doubles, necessitating the use of additional tools or configurations and/or external libraries

Here are three comparisons between Selenium and Karate, with code examples, highlighting how Karate simplifies test automation compared to Selenium

Handling Web Elements: Selenium requires explicit commands to interact with web elements, such as finding elements by ID, XPath, or CSS selectors. In contrast, Karate offers a more straightforward approach using a simple syntax. Here’s an example of clicking a button using Selenium and Karate:


WebElement button = driver.findElement(By.id("myButton"));


* click('#myButton')

Assertion and Verification: Selenium relies on various assertion libraries (e.g., TestNG or JUnit) to verify expected outcomes. This often involves writing additional code or importing external libraries. Karate, on the other hand, provides built-in assertion capabilities that simplify the process. Here’s an example of verifying the text of an element using Selenium and Karate:


WebElement element = driver.findElement(By.id("myElement"));
String actualText = element.getText();
assertEquals("Expected Text", actualText);


* def actualText = text('#myElement')
* match actualText == 'Expected Text'

Handling API Requests: Selenium primarily focuses on web automation and doesn’t provide native support for API testing. To perform API testing with Selenium, additional libraries (For example; Rest-Assured) or tools are required. Karate, on the other hand, seamlessly integrates API testing within the same framework. Here’s an example of making an HTTP request using Selenium with the RestAssured library and Karate:

Selenium with RestAssured:

Response response = RestAssured.get("https://api.example.com/users/1");
int statusCode = response.getStatusCode();
assertEquals(200, statusCode);


Given url 'https://api.example.com'
When get 'users/1'
Then status 200

These code comparisons demonstrate the simplicity and ease of use provided by Karate compared to Selenium. Karate’s intuitive syntax and built-in capabilities significantly reduce the amount of code and external dependencies required for test automation, making it a more straightforward and efficient choice for testers and developers.

Conclusion: While Selenium has been a dominant force in the test automation landscape, Karate offers several compelling reasons to make a switch. With its simplicity, native API testing support, built-in test reports and debugging, data-driven testing capabilities, and integrated test doubles, Karate provides a powerful and versatile framework for test automation. By embracing Karate, organizations can streamline their testing efforts, enhance productivity, and achieve more comprehensive and reliable test coverage.

Here are the reference links to Karate’s GitHub repository, official website, and other relevant resources:

    1. Karate GitHub Repository:https://github.com/karatelabs/karate
    2. Karate Official Website: https://karatelabs.io/
  1. Karate Documentation: https://github.com/karatelabs/karate#readme
  2. Karate Examples: https://github.com/karatelabs/karate-examples/blob/main/README.md
  3. Karate API Testing: https://github.com/karatelabs/karate/tree/master/karate-demo
  4. Karate Parallel Execution: https://github.com/karatelabs/karate#parallel-execution
  5. Karate Data-Driven Testing: https://github.com/karatelabs/karate#data-driven-features
  6. Karate LinkedIn: https://www.linkedin.com/company/karatelabs/
  7. Karate Udemy course: https://www.udemy.com/course/karate-dsl-api-automation-and-performance-from-zero-to-hero/

By exploring these resources, you can dive deeper into Karate’s features, syntax, and best practices, helping you make an informed decision about transitioning from Selenium to Karate for your test automation needs.