Generate API contract tests from examples

Turn API examples and schemas into starter contract test assertions so teams can catch response-shape regressions earlier.

Open this example in API Contract Test Generator

Open the tool, then paste the sample input below. Everything runs locally in your browser.

Open this example in API Contract Test Generator →

The problem

Manual API tests often check only status codes. Contract tests should also verify required fields, types, headers, and response shape so client integrations fail fast when an API changes unexpectedly.

Sample input

API example
GET /users/123
200 OK
{ "id": "123", "email": "user@example.com", "active": true }

Expected output

Starter test outline
Assert status is 200
Assert body.id is string
Assert body.email is string
Assert body.active is boolean

How to do it

  1. Paste an API response example or schema.
  2. Choose the target test style if available.
  3. Generate the starter assertions.
  4. Review field and type checks.
  5. Copy the result into your test suite.

Common mistakes

  • Testing only HTTP status codes.
  • Overfitting tests to volatile values such as timestamps.
  • Forgetting negative cases and error responses.
  • Checking examples that do not match the published schema.

Related tools

FAQ

What should an API contract test assert?

At minimum, check status, required fields, field types, important headers, and known error shapes.

Should I assert every response value?

Usually no. Assert stable contract fields and avoid brittle checks for timestamps, generated IDs, or ordering unless they matter.

Is the API example uploaded?

No. Test generation runs locally in your browser.

Is my data uploaded anywhere?

No. This workflow runs locally in your browser unless you explicitly copy or share the result yourself.

This guide uses browser-local tooling. Avoid pasting production secrets unless you understand what the tool displays and shares.

Explore related tools

Continue with adjacent browser-based tools for the same workflow.

View API contract tools →

Generate API contract test ideas: quick answer

Use this when an endpoint example or schema needs repeatable checks before release. Paste or load the artifact into the linked tool, run the local check, then copy only the safe result or summary into your PR, ticket, or test notes.

What to verify

Cover status codes, required fields, type boundaries, nullable fields, error shapes, auth behavior, and backward compatibility expectations. If a result will be shared outside your team, run a privacy or secret scan first and replace real values with safe examples.

Recommended next steps

Practical example and expected result

Turn API examples and schemas into starter contract test assertions so teams can catch response-shape regressions earlier. In practice, this is most useful when you need a quick, repeatable check on a developer artifact before adding it to a ticket, pull request, test fixture, or support note.

A realistic input for this workflow is GET /users/123 200 OK { "id": "123", "email": "user@example.com", "active": true }. The expected result should resemble Assert status is 200 Assert body.id is string Assert body.email is string Assert body.active is boolean, with the same important values preserved.

Troubleshooting checklist

  • Confirm you copied the complete developer artifact and not only a partial line or truncated preview.
  • Run the local tool once with a safe sample, then repeat with the real data only if your team policy allows it.
  • Check quoting, escaping, whitespace, encoding, timestamps, and environment-specific values before trusting the result.
  • Before sharing output, remove secrets, tokens, cookies, customer data, and production hostnames that are not needed for the review.

Next useful steps