API Contract Testing

For this contract testing example, I used JSONPlaceholder to validate that required fields exist and follow the expected data types, ensuring a consistent API contract and preventing breaking changes.

Step to Reproduce:

1. Create a GET request in Postman using https://jsonplaceholder.typicode.com/posts/1
2. Send the request and capture the JSON response
3. Add tests to validate required fields and data types.
4. Verify that the response structure remains consistent across executions.

API Contract Testing Workflow:

Testing Execution in Postman:

1. Send GET request to /posts/1
2. Validate fields such as userId, id, title, and body
3. Check that each field matches the expected data type
4. Confirm that the response contract is stable.

What This Demonstrates:

• API contract validation
• Response structure consistency
• Required field and type verification
• Detection of breaking changes between API consumers and backend.

“Consistency in structure is what keeps systems connected.”