Response body assertions in Postman - Build an Automation Script

Verify response body contains expected user data

Preconditions (2)

Step 1: Send a GET request to https://api.example.com/users/123

Step 2: Check the response status code is 200

Step 3: Verify the response body contains a JSON object with keys: id, name, email

Step 4: Verify the id value is 123

Step 5: Verify the name value is 'John Doe'

Step 6: Verify the email value is '[e-mail]'

✅ Expected Result: Response status code is 200 and response body JSON contains correct user data as specified

Automation Requirements - Postman Tests

Assertions Needed:

Status code is 200

Response body has keys: id, name, email

id equals 123

name equals 'John Doe'

email equals '[e-mail]'

Best Practices:

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

Use pm.response.json() to parse response body

Use strict equality checks for values

Write clear and descriptive assertion messages

Automated Solution

Postman

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

pm.test('Response body has expected user data', () => {
    const jsonData = pm.response.json();
    pm.expect(jsonData).to.have.all.keys('id', 'name', 'email');
    pm.expect(jsonData.id).to.eql(123);
    pm.expect(jsonData.name).to.eql('John Doe');
    pm.expect(jsonData.email).to.eql('[e-mail]');
});

The first test checks that the response status code is exactly 200 using pm.response.to.have.status(200). This ensures the request was successful.

The second test parses the response body JSON with pm.response.json(). It then asserts the JSON object has all the keys id, name, and email using to.have.all.keys. This confirms the expected data structure.

Finally, it checks each key's value matches the expected data using strict equality to.eql(). This verifies the correctness of the response content.

Each assertion has a clear message to help identify failures during test runs.

Common Mistakes - 4 Pitfalls

Not checking the status code before validating response body

Using loose equality (==) instead of strict equality (=== or to.eql) in assertions

Not parsing the response body JSON before accessing keys

Hardcoding values without verifying the response structure first

Bonus Challenge

Now add data-driven testing with 3 different user IDs and expected user data

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