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Schema Validation & Schema Generation

Restlyn supports optional contract testing via JSON Schema validation. It also automatically generate JSON schema from live responses.

📌 Schema Validation...How It Works​

When a Gherkin step includes:

Then response should match schema "userSchema"

Restlyn will:

  1. Load the userSchema.schema.json from your schemas/ folder
  2. Validate the response using AJV
  3. Fail the test if the schema doesn’t match

📁 Default Schema Location​

All schemas are expected under:

schemas/

You can override this using:

restlyn tests --schemas ./custom-folder

🧾 Schema Validation Errors​

If validation fails during a test:

  • ❌ Missing fields are listed
  • ⚠️ Extra/unexpected fields are shown
  • Detailed AJV error messages are printed

🧬 Generate a Schema Automatically​

Use the CLI command:


restlyn schema --url /profile --method GET --output userProfile --env local

restlyn schema --url /profile --method GET --output userProfile --env local \
--headers '{"Authorization":"Bearer mocked-token-123"}'

Optional flags:

  • --method, --headers, --body, --env

Restlyn will:

  • Fetch the live API response

  • Convert it to a basic JSON schema

  • Save to schemas/userProfile.schema.json

  • Small notes:

    By default, schemas are looked up under paths.schemas in your .restlynrc (falls back to ./schemas). The restlyn tests command also lets you override with --schemas dir.

    The schema CLI builds the full URL from .restlynrc’s baseUrls.local or baseUrls.prod depending on --env. If you pass an absolute --url, it will use it as-is.

🔍 Strict vs Lenient (Upcoming)​

Future versions will support --strict flag to:

  • Fail on extra fields (currently allowed)
  • Enforce exact schema match

Use schemas to ensure your API contracts don’t silently break!

➡️ Next: Data-Driven Testing