Karate — Unified API and UI Test Automation in Plain Text

Introduction

Karate is a test automation framework created by Intuit that unifies API testing, UI testing, mocking, and performance testing into a single tool. Tests are written in a readable plain-text syntax based on Gherkin, but unlike Cucumber, no step definitions or glue code are needed. Karate is built on Java but requires no Java knowledge to write tests.

What Karate Does

• Tests REST, SOAP, and GraphQL APIs with built-in JSON/XML assertion support
• Automates browser UI testing via an embedded Chrome DevTools Protocol driver
• Mocks HTTP services for contract testing and local development
• Runs performance tests by re-using functional test scripts with Gatling integration
• Supports parallel execution and generates rich HTML reports

Architecture Overview

Karate parses .feature files written in a Gherkin-like DSL and executes steps through a built-in step-definition engine. For API tests, it uses an HTTP client to send requests and match responses using a powerful JSON path expression syntax. For UI tests, Karate embeds a Chrome DevTools driver. The framework runs on the JVM, leverages JUnit 5 for test discovery, and uses a custom parallel runner that distributes scenarios across threads.

Self-Hosting & Configuration

• Add Karate as a Maven or Gradle dependency in a Java project
• Requires Java 11 or higher; no other runtime dependencies
• Place .feature files alongside a minimal JUnit runner class
• Configure karate-config.js for environment-specific URLs and variables
• Use karate.env system property to switch between dev, staging, and production

Key Features

• No step definitions needed: the DSL has built-in keywords for HTTP, JSON, XML, and assertions
• Embedded JSON and XML support with powerful match expressions (match ==, match contains)
• Data-driven testing via Scenario Outline and Examples tables
• Built-in HTTP mock server for contract testing without external tools
• Re-use API tests as performance tests with Gatling integration

Comparison with Similar Tools

• REST Assured — Java library for API testing; Karate requires no Java code and includes UI, mocks, and perf testing
• Postman/Newman — GUI-first API testing with collection runner; Karate is text-based and integrates natively with CI/CD
• Cypress — JavaScript web testing; Karate combines API and UI testing in one framework
• Cucumber — BDD framework requiring step definition code; Karate's steps are built in and need no glue code
• k6 — JavaScript-based load testing; Karate re-uses functional tests for performance without separate scripts

FAQ

Q: Do I need to know Java to use Karate? A: No, tests are written in a plain-text DSL. Java knowledge is only needed for advanced customizations.

Q: Can Karate test GraphQL APIs? A: Yes, send GraphQL queries as POST requests with a JSON body. Karate's JSON matching validates responses natively.

Q: How does Karate handle authentication? A: Use karate-config.js to set auth tokens or headers globally, or use callonce to run a login flow and share tokens.

Q: Does Karate support CI/CD integration? A: Yes, Karate runs as standard JUnit tests and produces JUnit XML reports compatible with any CI system.

Sources

• https://github.com/karatelabs/karate
• https://karatelabs.github.io/karate/