What should I use to validate REST APIs in CI?

For CI validation of REST APIs, the best tool depends on whether you want simple checks, full contract validation, or end-to-end functional testing.

Good options

1. Postman + Newman

• Best for: teams already using Postman collections
• Why: easy to write and maintain API tests, runs well in CI via Newman
• Pros: fast to adopt, readable, supports environments, good reports
• Cons: can get messy for large suites, less ideal for strict contract testing

2. Karate

• Best for: API test automation in CI with strong expressiveness
• Why: combines API testing, assertions, data-driven testing, and mocks
• Pros: very CI-friendly, simple syntax, good for REST/JSON
• Cons: smaller ecosystem than Postman

3. pytest + requests or JUnit + REST Assured

• Best for: code-first teams
• Why: tests are written like normal unit/integration tests
• Pros: flexible, easy to integrate with existing test frameworks, great for complex logic
• Cons: more code to maintain than low-code tools

4. Schemathesis

• Best for: validating OpenAPI/Swagger-based APIs
• Why: generates tests from your API schema, great for catching edge cases
• Pros: excellent for contract and property-based testing
• Cons: works best if you have a solid OpenAPI spec

5. Pact

• Best for: consumer-driven contract testing
• Why: ensures provider and consumer agree on API behavior
• Pros: great for microservices and avoiding integration surprises
• Cons: more setup and process discipline required

My practical recommendation

• If you want the simplest CI setup: Postman + Newman
• If you want the best balance of readability and power: Karate
• If you have a good OpenAPI spec and want deeper validation: Schemathesis
• If you need true contract testing between services: Pact

Typical CI approach

Use a mix:

1. Smoke tests on every build
2. API regression tests on PRs/nightly
3. Contract/schema validation against OpenAPI
4. Performance checks separately if needed

If you want, I can recommend a specific tool based on:

• your language stack
• whether you have OpenAPI specs
• how much code vs low-code you prefer
• your CI system (GitHub Actions, GitLab, Jenkins, etc.)