Stop waiting for dependent services. Karate lets you write API mocks in the exact same Gherkin syntax as your tests — 100% local, version-controlled, and thread-safe. One framework for both sides of the contract.
Feature: User Service Mock
Background:
* def users = []
Scenario: pathMatches('/users') && methodIs('post')
* def user = request
* user.id = users.length + 1
* users.push(user)
* def responseStatus = 201
* def response = user
Scenario: pathMatches('/users') && methodIs('get')
* def response = users
Scenario: pathMatches('/users/{id}') && methodIs('get')
* def response =
users.find(u => u.id == pathParams.id)Features
Same syntax. Same IDE. Same repo. Your mocks live next to your tests — version-controlled, reviewable, and shareable across the team.
Runs on your laptop, your CI runners, or your staging environment — never in the cloud. Mock payloads and secrets never leave your infrastructure.
Stateful mocks, conditional logic, and path parameter matching — all in pure Karate syntax. Build realistic service doubles without custom code.
Plain-text .feature files that diff cleanly in PRs. Mocks evolve with your codebase, not in a separate cloud tool.
Handles concurrent requests out of the box — perfect for powering performance tests or running alongside parallel integration tests without race conditions.
Start and stop mocks programmatically inside unit tests, or run them standalone from the command line. Full control over mock lifecycle for any workflow.
Gherkin scripts with IDE highlighting. No Java required, no new tool to learn — if your team writes Karate tests, they already know how to write Karate mocks.
Use Cases
The real-world situations where Karate mocks earn their keep.
When you can't block on another squad's service being ready, mock their contract and move forward. Swap in the real service later without changing your tests.
Stop chasing flaky staging environments. Mock the unstable external service locally, make your tests deterministic, and ship with confidence.
Drive load tests against a mock instead of staging. Thread-safe design means you can hammer the mock with thousands of concurrent requests without surprises.
Design the API contract, build the mock first, and let frontend/backend teams develop in parallel against the same simulated endpoint.
Comparison
Stack up unified test + mock against dedicated mocking tools.
| Capability | Karate Mocks | WireMock | Postman Mocks |
|---|---|---|---|
| Same syntax as tests | Yes — unified | No (Java / JSON config) | No (separate UI) |
| 100% self-hosted | Yes | Yes | No (cloud only) |
| Dynamic / stateful responses | Full JS-powered logic | Via extensions | Limited |
| Thread-safe parallel requests | Built-in | Yes | Rate-limited |
| Git-friendly version control | Plain-text .feature | JSON stub files | Cloud workspace |
| Learning curve | Same as Karate tests | Java + DSL | Postman UI |
| Embed in unit tests | Lifecycle API | Yes | No |
| Open source | Yes — MIT | Yes | Freemium |
Write your tests. Mock your dependencies. Run them side by side. All in the same syntax, the same repo, the same team.