Karate? Isn’t that a Japanese martial art? Yes! But karate is also an extremely popular testing framework in the IT community. In our projects, we repeatedly deal with large, monolithic software systems that we’re migrating to a modern cloud environment with microservices. Our quality assurance team has put various testing frameworks through their paces in different use cases and, admittedly, was a little surprised itself by what this “Karate” is capable of.
Especially in complex software projects with a monolithic structure and rapidly scaling user numbers, it may eventually become necessary to break up this monolith and separate out the individual business domains. This is precisely where Karate helps us ensure a smooth separation of the individual areas into functional microservices. But what exactly is Karate?
What is karate?
As mentioned earlier, this is a testing framework. Karate was developed specifically for API and web service automation and offers a simple yet powerful solution for building automated tests for web applications. Above all, the ability to write tests in clear, natural language—which allows even non-developers to be involved in the testing process—makes Karate the tool of choice for many.
Launched in 2017 by Peter Thomas, the open-source version quickly generated a buzz that continues to this day. The application combines the following features into a single framework: API test automation, API mocking, UI test automation (a mix of UI and API tests is possible), and performance testing. The tests are written in the language-neutral Gherkin, which makes them easy to understand and clearly structured. This also benefits developers, as it significantly reduces the cognitive load and allows resources to be allocated elsewhere.
Behavior-Driven Development
The Gherkin syntax has its origins in Behavior-Driven Development (BDD). This is a method used in agile software development that describes and tests a system’s behavior from the user’s perspective. At the heart of the method is the early involvement of everyone involved in the project—such as developers, testers, subject matter experts, and stakeholders—to establish a common language and a shared understanding. BDD strengthens collaboration between quality management and business analysis.
In BDD, use cases are defined collaboratively; these are referred to as scenarios. These scenarios describe the desired behavior of the software. To test this behavior, mock objects are created to simulate the actual behavior of the software. Tests are then developed against these mock objects and gradually replaced by the actual software logic until the software is finalized. This core concept forms the foundation of the BDD approach.
Karate incorporates these BDD principles, among others, and thus offers an easy-to-read, Gherkin-based syntax for describing test scenarios in natural language. This allows developers, as well as business analysts and project management teams, to contribute to the test description and precisely define the system’s behavior. But what exactly do these Karate tests look like, and what is it that makes them so appealing?
API & UI Testing
Karate offers powerful features for API testing and testing UI components.
For API testing, Karate allows you to send HTTP requests and verify responses. It also supports testing at various levels (XML, JSON, etc.), including interaction with databases and external services, to perform comprehensive API testing and verify the behavior of the interfaces in various scenarios.
Our experts have developed a brief example of an API test that evaluates two scenarios. In the first scenario, a GET request is sent for the user details with ID 123, and the test verifies whether a status code of 200 is returned and whether the expected user response matches. In the second scenario, a POST request is sent to create a user, and the test verifies whether a status code of 201 is returned and whether the generated user response contains a numeric ID.
API Test
Called API
This example also serves as an excellent illustration of the influences and benefits of BBD in karate. The terms given, when, then and and These terms come from the Gherkin syntax and, even if you're not familiar with Karate, give you a general idea of what this test is about. Given here stands for the precondition, when for the action being performed and then for the system's expected response. And can be used in conjunction with other keywords to supplement them.
For UI testing, Karate enables interaction with graphical user interfaces (GUIs) by simulating web browsers. Developers can build test scenarios that include, for example, filling out forms, clicking buttons, and verifying the displayed information. The use of selectors makes it possible to identify and validate UI elements.
Our Xperts have also come up with an example for a UI test. In this test, a website is opened, the login form is filled out, and the login button is clicked. Then, the test verifies whether a welcome message is displayed.
Login
UI Test
A major advantage of Karate is that it seamlessly integrates API and UI testing. Developers can create test cases that cover both the behavior of APIs and that of the graphical user interface (GUI). This enables a comprehensive verification and prediction of a system’s end-to-end behavior. Using Karate for API and UI testing offers many benefits, such as improved test coverage, consistent syntax across all test types, and easy maintenance of tests over time. Karate also enables the creation of comprehensive test reports and a precise analysis of test results. Overall, Karate is a powerful solution for API and UI testing that helps developers deliver high-quality, highly reliable software.
How We Work
As a software service provider, we frequently work with clients whose software landscape consists of a complex monolith that has grown over the years. While such a structure may seem easier and more cost-effective to implement in the early stages, the challenges of ensuring trouble-free operation grow as the system expands. To ensure a functional system in the face of rapidly rising user numbers and features, a cloud migration using microservices is often unavoidable. As mentioned at the beginning, Karate helps us here by separating the individual business domains and transforming them into distinct microservices.
Before we extract a domain from the monolith, however, we must ensure that it can function independently of it. To do this, we write tests in Karate for the respective business domain, and if these tests pass, we extract the domain from the monolith and migrate it to a microservice. We then run the tests against the microservice as well. If the tests pass here too, we can be sure that everything is working smoothly. This means that all clients that previously used the monolith can be migrated to the microservice without any issues.
In addition to the benefits of decoupling individual domains and the enormous scalability, migrating to the cloud using microservices can also mitigate many other serious drawbacks of a monolithic software architecture. Nevertheless, when considering a migration, one must always weigh whether the initially higher costs are actually worth it. As a general rule: the larger the monolith, the more likely this is to be the case. So if you decide to migrate to the cloud, it’s all the more important that the migration is implemented smoothly and that you end up with fully functional microservices.
With its testing capabilities, Karate provides an almost perfect setup for this—though its use is by no means limited to cloud migrations. Due to its nature (Gherkin syntax, all-in-one solution, etc.) and its many integration options at various levels (e.g., XML, XPATH, JSON), Karate has established itself as the standard in many areas when it comes to fast and reliable testing.
