Request headers in Postman - Build an Automation Script

Verify custom request headers are sent and received correctly

Preconditions (2)

Step 1: Open Postman and create a new GET request

Step 2: Set the request URL to https://postman-echo.com/headers

Step 3: Add a custom header with key 'X-Test-Header' and value 'TestValue123'

Step 4: Send the request

Step 5: Observe the response body for the headers returned

✅ Expected Result: The response body contains the header 'X-Test-Header' with value 'TestValue123'

Automation Requirements - Postman/Newman

Assertions Needed:

Verify response status code is 200

Verify response JSON contains 'X-Test-Header' with value 'TestValue123'

Best Practices:

Use Postman test scripts to assert response values

Use environment variables for header values if needed

Keep tests independent and idempotent

Automated Solution

Postman

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

pm.test('Response contains custom header', function () {
    const jsonData = pm.response.json();
    pm.expect(jsonData.headers['x-test-header']).to.eql('TestValue123');
});

The first test checks that the HTTP status code returned is 200, meaning the request was successful.

The second test parses the JSON response body and verifies that the custom header 'X-Test-Header' is present with the exact value 'TestValue123'.

This ensures the header was sent and received correctly by the API.

Common Mistakes - 3 Pitfalls

{'mistake': 'Not setting the header key with correct casing', 'why_bad': 'Headers are case-insensitive but the API might return them in lowercase, causing assertion failures if case is mismatched.', 'correct_approach': "Use lowercase keys when accessing headers in response JSON, e.g., 'x-test-header'."}

Not checking the response status code before asserting header values

Hardcoding header values in multiple places

Bonus Challenge

Now add data-driven testing with 3 different custom header values

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