Karate Rest API Testing Example: A Detailed Guide for Developers

As more and more businesses rely on APIs to connect with customers, partners, and employees, it’s essential for developers to ensure the integrity and reliability of their APIs. Rest API testing is one of the most effective ways to ensure that your API functions as expected, and that it meets your performance and security requirements.

This article provides a detailed guide for developers on how to use Karate, a popular open-source testing tool, to test Rest APIs.

What is Karate?

Karate is an open-source, Java-based testing tool that enables developers to write automated tests for Rest APIs. Karate supports testing for REST, SOAP, JSON, GraphQL, and more. Karate is built on top of the widely-used Cucumber framework and is designed to be easy-to-use and flexible.

How to Set Up Karate on Your System?

Before starting with Karate Rest API testing, you need to set up Karate on your system. Here’s how you can do it.

1. Install Java Development Kit (JDK) version 8 or above.

2. Download the zip file from the Karate GitHub repository.

3. Extract the zip file into your desired location.

4. Add the ‘bin’ directory of the extracted folder to your system’s path.

5. Verify the installation by opening your terminal or command prompt and entering the following command:

„`
karate -version
„`

How to Write Your First Karate Test?

Once you have set up Karate on your system, you can start writing tests for your Rest APIs. Here’s how you can write your first Karate test using the sample Rest API from jsonplaceholder.typicode.com.

1. Open your text editor or IDE and create a new file named ‘sample-test.feature.’

2. Add the following code to the file:

„`
Feature: Sample REST API Test

Scenario: Verify GET response code
Given url ‚https://jsonplaceholder.typicode.com/posts‘
When method GET
Then status 200
„`

The above code defines a feature named ‘Sample Rest API Test.’ The feature contains a single scenario named ‘Verify GET response code,’ which verifies that the response to a GET request is 200.

3. Save the file and navigate to the directory where the file is saved using your terminal or command prompt.

4. Run the test by entering the following command:

„`
karate sample-test.feature
„`

If everything is set up correctly, you should see the following output in your terminal:

„`
1 Scenarios (1 passed)
3 Steps (3 passed)
0m1.248s
„`

The above output indicates that the test has passed, and the GET request returned a response with a status code of 200.

How to Write More Complex Karate Tests?

Now that you understand how to write a basic Karate test let’s take a look at some more advanced scenarios.

Verify Response Body

To verify the response body of the Rest API, you can use the ‘match’ keyword in Karate.

Here’s an example:

„`
Scenario: Verify response body

Given url ‚https://jsonplaceholder.typicode.com/posts/1‘
When method GET
Then status 200
And match response == {userId:1,id:1,title:“sunt aut facere repellat provident occaecati excepturi optio reprehenderit“,body:“quia et suscipit suscipit recusandae consequuntur expedita et cum reprehenderit molestiae ut ut quas totam nostrum rerum est autem sunt rem eveniet architecto“}
„`

The above code verifies that the GET request to the sample Rest API with the ID of 1 returns a response with a status code of 200, and that the response body matches exactly with the expected JSON object.

Passing Variables to a Karate Test

To pass variables to a Karate test, you can use the ‘Scenario Outline’ keyword in Karate.

Here’s an example:

„`
Scenario Outline: Verify Multiple Posts

Given url ‚https://jsonplaceholder.typicode.com/posts/‘
And path
When method GET
Then status 200

Examples:
| id |
| 1 |
| 2 |
| 3 |
„`

The above code executes the GET request for each value of ‘id’ provided in the table.

Frequently Asked Questions about Karate Rest API Testing Example

After introducing Karate Rest API Testing Example, there might be a few queries that need to be addressed to achieve a clear understanding. Here are some of the most frequent questions that people ask about Karate Rest API testing example.

1. What is Karate Framework?

Karate is an open-source framework that enables developers to create automated functional and UI tests for web services, as well as API testing. It is a simple, yet expressive tool that is easily readable and can test HTTP requests and responses. The Karate framework combines REST API, Generic Assertion Frameworks, and data-driven testing/data transformation to validate the API services.

2. What is Rest API Testing?

Rest API testing is a software testing process that checks the performance of the RESTful APIs. REST stands for Representational State Transfer, which communicates with applications using the HTTP protocol. The primary objective of API testing is to ensure that the basic functionality of the API is in compliance with the expectations.

3. Can Karate Framework be used for non-RESTful web services?

No, the Karate Framework is specifically designed for REST APIs only. However, its extensions are being developed to support GraphQL and Messaging service testing. Rest API relies on HTTP methods and the central idea of resources and representations, whereas, non-RESTful web services do not follow the REST guidelines aspect.

4. How to Install and Run Karate Framework?

Karate framework can be installed using the following step-by-step guide:

• Step 1: Install Java Development Kit (JDK) 8 or later version.
• Step 2: Install a build tool such as Apache Maven.
• Step 3: Create and open a Maven project in your IDE of choice.
• Step 4: Include the Karate Core dependency and relevant plugins in the pom.xml file.
• Step 5: Create a feature file that includes the test cases, and run the test cases with Maven.

5. How to write test cases using Karate Framework?

Karate allows the creation of test cases in plain English, called Gherkin syntax. A feature file is written, comprising multiple scenarios. Each scenario can be considered as a test case that states the steps to validate users, endpoints, headers, and assertions. The following is a small example of the feature file using Karate,

Feature: Users API

  Background:
    * url 'https://jsonplaceholder.typicode.com/users'

  Scenario: Retrieve all Users
    Given path ''
    When method get
    Then status 200
    And match response == read('users.json')

It tests a simple REST API to get users where the requests are set up in the ‚Given‘ section, the response’s expectation is defined in the ‚Then‘ section. The background represents the common settings, as the base URL in this case.

6. What Assertions Support Karate Framework?

Karate Framework supports various forms of valid assertions for both REST and SOAP APIs. The framework currently provides two primary mechanisms to assert the responses using JavaScript and Gherkin syntax. Some commonly used assertions in the Karate framework are:

• match
• contains only
• eval
• schemaValidation

7. What distinguishes Karate Framework from other testing frameworks?

Karate is an integrated testing framework for REST APIs. It also allows lightweight UI testing and integrations with database, messaging and service virtualisation tools. Unlike other frameworks, Karate does not require any setup configuration or external setup for its working. It runs inside a single self-contained Jar file, which demonstrates the convenience that the framework offers.

8. What are the best practices used in Karate testing?

The best practices to be followed for Karate testing include writing reusable code, maintaining the codebase, writing feature file containing scenarios, separating the code from data, and breaking test script into modules, etc.

9. What are the benefits of using Karate WebSocket as opposed to REST?

Karate WebSocket enhances the real-time data production, web-based chat applications, games, and stock market trading. They support bi-directional data transmission, long-lived connections, and messages sent by either end. REST API needs multiple requests to display the screen and the page refresh every time. In contrast, WebSocket enhances real-time communication.

10. What platforms are supported by Karate Framework?

Karate is a cross-platform tool that runs on MacOS, Windows, and Linux. It can be run from the command line, IntelliJ IDEA or any other Java IDE. Also, it supports the Docker container ecosystem and integrated with continuous integration and delivery pipelines.

Karate REST API Testing Example – A Step-by-Step Guide

Karate is an open-source testing framework that has gained popularity in recent years. It is designed specifically for testing APIs, and offers a powerful set of features that make it a popular choice among developers. In this blog post, we will provide a step-by-step guide on how to use Karate for REST API testing.

Step 1: Set up your Development Environment

Before you get started with Karate, you will need to set up your development environment. Here are the steps to follow:

• Install Java SDK (version 8 or higher)
• Download the Karate standalone JAR from https://github.com/intuit/karate/releases
• Add the JAR file to your classpath

Step 2: Create a New Test Suite

Once you have set up your development environment, you can create a new test suite using Karate. Here are the steps:

• Create a new folder for your test suite
• Create a new file called „karate-config.js“ in the folder you created
• Open a new file, and save it with the extension „.feature“. This file will contain your test scenarios.

Step 3: Write your First Test Scenario

Now that you have set up your test suite, you can start writing your first test scenario. Here is an example scenario that tests whether a GET request returns a 200 status code:

„`
Feature: Example API Test

Background:
* configure ssl = true

Scenario: GET Request Returns 200
Given url ‚https://your-api-url.com/api/endpoint‘
When method GET
Then status 200
„`

Step 4: Add Assertions to your Test Scenarios

In the example scenario above, we are only checking that the API returns a 200 status code. Typically, you will want to add more assertions to your test scenarios to verify the response body. Here is an example scenario that includes a JSON response body assertion:

„`
Scenario: GET Request Returns Expected Response Body
Given path ‚https://your-api-url.com/api/endpoint‘
When method GET
Then status 200
And match response == { name: ‚John‘, age: 25 }
„`

Step 5: Run your Test Suite

Once you have written your test scenarios, you can run your test suite using the Karate command-line runner. Here are the steps:

• Open your command prompt or terminal
• Navigate to the folder where your test suite is located
• Run the command „java -jar karate.jar your_test_suite_file.feature“
• Karate will execute your test suite and display the test results in the console.

Step 6: Automate your Test Suite

Finally, you can automate your test suite by integrating it with your Continuous Integration (CI) pipeline. Here are the steps:

• Set up your CI pipeline to run your test suite with Karate
• Configure your pipeline to send notifications if any of your tests fail
• Integrate your test suite with your build process

Conclusion

Karate is a powerful testing framework that offers a wide range of features for testing REST APIs. By following the steps outlined in this guide, you can easily set up your test suite, write your test scenarios, and run your tests. With Karate, you can automate your tests and ensure that your APIs are functioning as expected.