WireMock

WireMock is a tool for simulating HTTP APIs and other dependencies. Teams use it to test applications when the real services are slow, unavailable or not yet built.

WireMock lets you define stub responses that match requests by URL, headers, query parameters, cookies or body content. Responses can be built with Handlebars templates, so they include request data or random values. Traffic from a real service can be recorded and played back later for realistic tests. It can also simulate delays, network faults and malformed responses, which helps test how an application handles failure. Once the test is done, you can verify that the application sent the expected requests with the right parameters.

• Stub HTTP responses by URL, header, query or body
• Use Handlebars templates for dynamic responses
• Record real API calls and play them back
• Simulate delays, faults and malformed responses
• Verify the requests your application sent

Test engineers, QA teams and backend developers who write integration tests will find it valuable. Teams that work on features in parallel with other services can use it to keep development moving.

The core engine is free and open source under the Apache 2.0 license, and it can be self-hosted or embedded in your tests. Its Java and .NET documentation is the starting point for most users. A cloud platform with collaboration and advanced features is also available, and it has a free tier with no credit card needed.