JSON body in Postman - Build an Automation Script

Verify POST request with JSON body to create a new user

Preconditions (3)

Step 1: Open Postman and create a new POST request

Step 2: Set the request URL to https://api.example.com/users

Step 3: In the Body tab, select raw and choose JSON format

Step 4: Enter the following JSON body: {"name": "John Doe", "email": "[e-mail]", "age": 30}

Step 5: Send the request

Step 6: Observe the response status code and body

✅ Expected Result: Response status code is 201 Created and response body contains the created user details with name 'John Doe', email '[e-mail]', and age 30

Automation Requirements - Postman/Newman

Assertions Needed:

Verify response status code is 201

Verify response JSON body contains 'name' with value 'John Doe'

Verify response JSON body contains 'email' with value '[e-mail]'

Verify response JSON body contains 'age' with value 30

Best Practices:

Use environment variables for endpoint URLs

Use JSON schema validation for response body

Use descriptive test names

Use pre-request scripts if needed for setup

Avoid hardcoding sensitive data

Automated Solution

Postman

pm.test('Status code is 201', function () {
    pm.response.to.have.status(201);
});

pm.test('Response has correct user details', function () {
    const jsonData = pm.response.json();
    pm.expect(jsonData.name).to.eql('John Doe');
    pm.expect(jsonData.email).to.eql('[e-mail]');
    pm.expect(jsonData.age).to.eql(30);
});

The first test checks that the response status code is 201, which means the user was created successfully.

The second test parses the JSON response body and verifies that the 'name', 'email', and 'age' fields match the expected values sent in the request.

This ensures the API correctly processed the JSON body and returned the expected data.

Common Mistakes - 4 Pitfalls

Not setting Content-Type header to application/json

{'mistake': 'Using incorrect JSON syntax in the body', 'why_bad': 'Invalid JSON causes the request to fail or the server to return an error.', 'correct_approach': "Validate JSON syntax before sending; use Postman's raw JSON editor."}

Hardcoding URLs and data without using variables

Not verifying response status code

Bonus Challenge

Now add data-driven testing with 3 different user JSON bodies to create multiple users

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