What makes Karate stand out?
At its core, Karate is a test automation framework that is written in Java but does not necessarily require programming skills when used for basic software testing. It is heavily based on the Gherkin syntax, made famous by the Cucumber BDD framework. In fact, when it was first introduced to the software testing world, it was designed as an extension of Cucumber but quickly evolved into something of its own. However, some of Cucumber’s core characteristics are still evident and can be put to good use. For example, the very similar file structure, syntax, and compatibility with the standard JSON reporting format.
The first version was released on February 08, 2017, by Peter Thomas while he was working as a test engineer at Intuit India (https://www.intuit.com/in), a large software company in the fintech industry. His motivation was to come up with an easier-to-use and easier-to-understand API testing solution than the in-house framework his team was using at this time.
In Peter’s own words,
Thomas, P. (2017). Karate: Web-Services Testing Made Simple, https://medium.com/intuit-engineering/karate-web-services-testing-made-simple-366e8eb5adc0
Intuit suggested making his work open source in order to test how this new approach would be received by the community.
At the time of writing this book, the Karate framework sports more than 6.6k stars on GitHub (https://github.com/karatelabs/karate) and even received a GitHub grant for open source software in India.
Peter has apparently struck a nerve with the testing community!
In 2021, after this successful open source launch and adaption period, Peter decided to found Karate Labs (https://www.karatelabs.io), together with Kapil Bakshi, in order to work full-time on the further development and promotion of the framework and to offer some new paid products and services around Karate.
No paywall
The paid services by Karate Labs include subscription-based plugins for IntelliJ IDEA and Visual Studio Code with multiple tiers. In this book, however, we will focus exclusively on the freely available core framework and its various open source components and tools.
Interest in the Karate framework has not waned since then, as can be seen by the plethora of questions on Stack Overflow and its GitHub issues page. Since a lot of information is spread among many different online articles, social media channels, blog posts, and podcasts, I decided to write a book about it to provide a structured, comprehensive, and complete introduction.
In the upcoming sections, we will discover how Karate works in more technical and conceptual detail and what distinguishes this solution from other popular testing frameworks that may be more specialized but are also much harder to learn and use.
Also, we will further explore the similarities and differences between the classic Gherkin syntax and underlying concepts and Karate’s different approach in the next section. We will find out why certain decisions were made by the framework creator and why they were smart moves.
Discovering Karate’s strong points
Karate’s strengths lie in various areas of test automation, which we will discuss in this section. Later on in the book, we will shine a light on these different areas with a strong focus on the framework’s core purpose – testing APIs effectively.
Since there are multiple modules of Karate with different goals, let’s quickly walk through them to see how extensive the framework and its components have become over the years.
Testing APIs
Providing a basis for API tests that is easy to read and follow is the main capacity of Karate – it supports the REST, SOAP, and GraphQL APIs and can be extended to handle other types of APIs and data formats that are not as common. All other framework modules that cover different kinds of testing were gradually added and implemented with the same basic mechanisms and concepts. By focusing on its straightforward domain-specific Gherkin-based language, Karate can map a lot of API test functionality without having to write elaborate code for communicating with web services or handling various payloads and data exchange formats.
Additionally, Karate includes many powerful assertions to verify response data, and its structure, especially JSON and XML, are handled exceptionally well. This makes it a perfect fit for a lot of modern APIs that use these formats.
We will explore all of this in Chapter 3, Writing Karate Tests.
Fun fact
Even though Karate is often associated with JSON, XML support was implemented first in its initial prototype before JSON handling was added!
Test doubles
Testing microservice infrastructures or web services calling other services or databases can get very complex and challenging. Typically, the approach is to spin up all components that make up a full system in order to test it thoroughly. This makes it hard to run tests for a single component because each test needs to go through multiple layers. This means that other dependent services need to be very predictable and reliable in such a setup so you can obtain meaningful and non-flaky test results.
Test doubles, a term coined by agile software development consultant Gerard Meszaros (http://xunitpatterns.com/gerardmeszaros.html), solve this problem. It groups together all forms of fake objects (or fake APIs) that can be used instead of real objects in tests. They behave as if you were making real requests and data transfers but deliver the same predictable responses every time. This allows you to perform testing on a small part of the system without having to directly use all real dependencies and services. Thus, the tests can run faster and more securely because you are not affected by network problems, bad connections, database inconsistencies, and other failures.
Karate can define such doubles easily using nothing but Gherkin, as we will see in Chapter 6, More Advanced Karate Features!
Performance tests
Karate’s main strength in the performance testing field is that it can reuse existing scenarios. The same test cases that are used as acceptance tests can seamlessly act as Gatling performance tests. This means that it is possible to simulate multiple clients or connections that interact with your APIs in order to check their resilience and how they hold up under heavy loads. By integrating the popular Gatling framework, Karate gains a huge advantage here because it frees us from using completely separated solutions, third-party frameworks, and libraries that would require additional research, learning, and onboarding.
Also, due to its ability to reuse already implemented test scenarios, we do not need to spend time and resources duplicating them in another programming language just for the sake of performance tests.
In Chapter 10, Performance Testing with Karate Gatling, we will look deeper at this important testing topic.
Browser automation
The automation of websites and browser-based user interfaces has become much more important in recent years. More and more user-facing software is available as web applications, which can be very complex in design. Also, a lot of functionality and logic can be wired into the frontend, making it necessary to thoroughly test this area as well.
Karate UI is special here because it combines the Chrome DevTools Protocol (CDP) and the WebDriver protocol, so it can accomplish pretty much everything that other popular tools such as Selenium, Cypress, and Playwright can do.
As we will see in Chapter 9, Karate UI for Browser Testing, this module was one of the last ones added to the Karate framework to cover this testing field as well. Among other things, it provides full debugging capabilities and even allows freely mixing API and UI automation to handle even more complex use cases.
Desktop automation
Karate also supports automating desktop applications through its integration with the Robot framework. This is an entirely different use case than the other ones that are discussed in this book, but maybe this will contribute to your decision to give Karate a try.
If you want to know more about this part of Karate, check the documentation at https://github.com/karatelabs/karate/tree/master/karate-robot.
Now that we have gotten to know Karate’s core uses, let’s find out about its main features next.
Core features
Since many useful and often needed functions of other specialized test frameworks are already implemented in the core framework, you will reach useful results fast and without a steep learning curve. This makes Karate ideal for quickly implementing a large number of test cases and working off low-hanging fruits (things that take only a little time while having a great benefit).
Karate’s big advantage is the consistent syntax across test types. This makes switching between different test projects and contexts easier and faster, as there is no need for extensive training. Also, it keeps the test suites very clean, easy to understand, and maintainable when written well.
If, however, you require expanded functionality, you are free to add it as either Java or JavaScript code, depending on which language features can solve your problem better and your respective skills with each of them.
Let’s look at some of its most useful aspects!
Parallel test execution
Often, extensive test suites contain a lot of different scenarios that differ greatly in individual runtime. Executing these tests in sequence, meaning one after the other, can lead to an unnecessarily long feedback time. Many other test frameworks have parallelization built in, at best, as an afterthought or require additional tools for this. Also, it can be complex to execute and evaluate (for example, because test reporting cannot deal with parallel scenarios correctly). Karate has this approach on board as a basic feature for all different test types.
As we will later see in Chapter 4, Running Karate Tests, we will even be able to visualize and track how tests are run on different threads, making this a powerful option for more efficient test runs.
Data-driven testing
In Chapter 3, Writing Basic Karate Tests, we will discover that the Karate framework even supports data-driven tests. That means that one or more test scenarios can be reused with multiple sets of data instead of writing separate ones for each individual use case. This reduces code duplication and errors caused by having to change multiple code locations across a lot of feature files if requirements change.
The unique aspect of Karate in this regard is that these records of data can even be defined in JavaScript Object Notation (JSON) or comma-separated values (CSV) formats. Also, they are not required to be static data as in a Cucumber-based framework but can be generated dynamically.
Auto-generated test reports and logs
Karate has its own built-in reporting library that generates informative HTML-based test reports that show what features and scenarios were run along with requests, responses, and additional information such as tags, screenshots, and even a timeline of parallel runs. These help greatly in analyzing test runs and can act as a form of documentation as well. In case you need to display custom information, Karate even includes a full templating engine that can be programmed to display any additional data you may need.
Additionally, all Karate actions, up to every single request and response, are logged. Even with the most beautiful test reports, it is often simple text logs that provide the most information about errors that have occurred.
We will encounter both variants of debugging, including custom configuration and extension, in Chapter 5, Reporting and Logging.
First-class support of common data formats
Karate, through its Java and JavaScript roots, can handle pretty much any data format found on the web today. This does not only mean processing them but also making assertions, performing schema validations, and efficient fuzzing matching of results. Later in this chapter, we’ll take a closer look at the formats that are natively supported. Additionally, we will explore this topic further in Chapter 3, Writing Basic Karate Tests, and Chapter 4, More Advanced Karate Features.
Beginner friendliness
One of the best characteristics of the Karate framework is that it allows users to start using it as a solution where no coding is necessary and gradually realize more complex test cases by writing Java or JavaScript code on top of it. The Karate domain-specific language (DSL) will be discussed in more detail a little later in this chapter.
When using Karate, it is worth mentioning that it is usually just one single dependency you need that covers most functionality (for example, API testing, UI testing, and performance tests), making this rather simple to set up.
Additionally, there is even a standalone executable version of Karate that can do everything that the Java library can do but without requiring experience with setting up a Java project. This is useful for quickly trying out Karate without extensive preparation. For a production environment, I would nonetheless recommend the Maven setup that we will see in Chapter 2, Setting Up Your KarateProject, and Chapter 4, Running Karate Tests.
Built-in support of different environments
If you have a mature test suite, the goal is typically to run it within a continuous delivery pipeline on different development environments, for example staging, user acceptance, and live. Often, these environments have different URLs, endpoints, access rules, and configurations. So, it is very convenient if the test framework offers a simple way to keep these configurations inside the test repository and switch easily between them.
Karate offers this as a native functionality as we will see in Chapter 6, More Advanced Karate Features.
Read-eval-print loop
A read-eval-print-loop (REPL) is a programming environment that reads user inputs, then processes and executes them as code snippets and prints the results. Karate has a command-line REPL, which allows test code to be inserted or replaced at runtime, making it easier and faster to develop tests. This can save time that would otherwise be spent modifying, adapting, and executing a complete test scenario repeatedly. The REPL is a main component of Karate’s Visual Studio Code plugin and can also be used for UI tests!
One framework for all
All previously mentioned features are anything but self-evident, and it is an accomplishment not to be undersold that they come together here in one integrated software testing solution!
In this section, we looked at Karate’s main use cases and features that make it stand out from other frameworks. Next, we will turn to an aspect of the framework that is controversial to some testers – the difference between the BDD approach and how Karate takes this idea and changes it.