JSON Schema validation in Postman - Build an Automation Script

Validate API response against JSON Schema

Preconditions (2)

Step 1: Send a GET request to the API endpoint https://api.example.com/users/1

Step 2: Wait for the response

Step 3: Validate the response body against the provided JSON Schema

✅ Expected Result: The response body matches the JSON Schema and validation passes

Automation Requirements - Postman test scripts

Assertions Needed:

Response status code is 200

Response body matches the JSON Schema

Best Practices:

Use pm.response.to.have.status for status code assertion

Use pm.response.to.have.jsonSchema for schema validation

Keep JSON Schema clear and minimal

Write clear and descriptive test names

Automated Solution

Postman

pm.test('Status code is 200', () => {
    pm.response.to.have.status(200);
});

const userSchema = {
    type: 'object',
    required: ['id', 'name', 'email'],
    properties: {
        id: { type: 'integer' },
        name: { type: 'string' },
        email: { type: 'string', format: 'email' }
    }
};

pm.test('Response matches JSON Schema', () => {
    pm.response.to.have.jsonSchema(userSchema);
});

The first test checks that the response status code is 200, which means the request was successful.

The userSchema defines the expected structure of the JSON response: an object with id as an integer, name as a string, and email as a string in email format.

The second test uses Postman's built-in jsonSchema assertion to verify the response body matches this schema exactly.

This approach ensures the API returns data in the correct format and helps catch errors early.

Common Mistakes - 3 Pitfalls

Not checking the response status code before schema validation

Using an incomplete or incorrect JSON Schema

Hardcoding values in the schema that change frequently

Bonus Challenge

Now add data-driven testing with 3 different user IDs (1, 2, 3) to validate their responses against the JSON Schema

Show Hint