Practice Exercises

Time to put everything into practice. These exercises go from simple to complex. Do them in order. Each one builds on the previous.

Exercise 1: Write a Schema from Scratch

Hit GET https://jsonplaceholder.typicode.com/posts/1 and write a JSON Schema from scratch for the response. Include: required fields, correct types, minimum values for IDs, and minLength for strings.

// Expected response shape:
{
  "userId": 1,
  "id": 1,
  "title": "sunt aut facere ...",
  "body": "quia et suscipit ..."
}

Exercise 2: Validate in Postman with Ajv

1. Create a GET request to https://jsonplaceholder.typicode.com/users/1 in Postman
2. Write a complete schema for the user response (including nested address and company objects)
3. Validate using Ajv in the Tests tab with allErrors: true
4. Intentionally break the schema (change "id" type to "string") and observe the error message
5. Fix the schema and verify the test passes

Exercise 3: Validate Array Response

1. Hit GET https://jsonplaceholder.typicode.com/posts
2. Write a schema with root type "array" and items schema for each post
3. Add minItems: 1 to ensure the array is not empty
4. Validate in Postman using both tv4 (with checkRecursive=true) and Ajv
5. Compare the error output between tv4 and Ajv when validation fails

Exercise 4: REST Assured Schema Validation

1. Create a Maven project with REST Assured and json-schema-validator dependencies
2. Create a schemas/ folder inside src/test/resources/
3. Write a schema file for GET /comments (nested postId, id, name, email, body)
4. Write a TestNG test that validates the response using matchesJsonSchemaInClasspath()
5. Run the test — it should pass
6. Modify the schema to make it fail (e.g., change body type to "integer") and observe the error

Exercise 5: Banking Portal Schema

Write a complete schema for the Banking Portal login response. The response includes userId, token, account details with nested holder and address, and a transactions array. Use enum for accountType, pattern for PAN and phone, and additionalProperties: false. Validate in both Postman and REST Assured.

Exercise 6: Auto-Generate and Refine

1. Hit GET https://jsonplaceholder.typicode.com/users/1 and copy the response
2. Paste it into https://www.jsonschema.net/ to auto-generate a schema
3. Compare the auto-generated schema with one you would write manually
4. List 5 things the auto-generated schema is missing (required, constraints, patterns, etc.)
5. Tighten the schema manually and test it