Cucumber.js vs WSO2 Contract Test Runner

Cucumber.js checks software against executable specifications written as plain-text scenarios, reporting whether each scenario passes or fails. It is the JavaScript implementation of Cucumber and runs on Node.js. Scenarios use Gherkin syntax and are usually kept in `.feature` files alongside the software in source control. Step definitions connect each Gherkin step to code that carries out its described action; expressions can use Cucumber Expressions or regular expressions, but not both syntaxes in a single expression.

The tool runs feature files from the command line and can run in continuous integration, including parallel execution. Reporter plugins can produce results, and reports can be published to Cucumber Reports with `--publish`. Published reports are public and deleted after 24 hours. Cucumber.js is available as the `@cucumber/cucumber` npm module, installed as a development dependency with npm or Yarn. The setup requires Node.js and one of those package managers. It is free and open source, with Linux, macOS, Windows, and self-hosted platforms listed. It works with browser automation tools, but is not itself one.

WSO2 Contract Test Runner is a free, Apache-2.0-licensed library for consumer-based testing of live REST API endpoints. It sends requests and compares returned data with expected responses defined in JSON contracts. A contract can include a request, expected response, assertions, and optional post-conditions. Assertions cover status codes, JSON body and header paths, exact values, regular expressions, emptiness, structures, arrays, and objects. Tests run through Docker by mounting contract and configuration files into the documented image workflow. Suites can run contracts before or after tests, with before-suite contracts running synchronously. Post-conditions can place extracted values into suite-scoped or global environment variables, and contracts can pause for a specified number of seconds. The sample setup uses bearer authorization, cookies, a certificate keystore, and a client truststore. XML path support is listed as a todo. Deployment is Linux and self-hosted.