API versioning validation in Postman - Build an Automation Script

Validate API versioning in the response header

Preconditions (3)

Step 1: Send a GET request to the API endpoint with version v1 in the URL (e.g., https://api.example.com/v1/resource)

Step 2: Check the response status code is 200

Step 3: Verify the response header 'API-Version' exists

Step 4: Verify the 'API-Version' header value is 'v1'

Step 5: Send a GET request to the API endpoint with version v2 in the URL (e.g., https://api.example.com/v2/resource)

Step 6: Check the response status code is 200

Step 7: Verify the response header 'API-Version' exists

Step 8: Verify the 'API-Version' header value is 'v2'

✅ Expected Result: The API responds with status 200 for both versions and the 'API-Version' header matches the requested version.

Automation Requirements - Postman Test Scripts

Assertions Needed:

Response status code is 200

'API-Version' header exists

'API-Version' header value matches requested version

Best Practices:

Use pm.test for assertions

Use pm.response to access response data

Write clear and descriptive test names

Avoid hardcoding URLs inside tests; use environment variables if possible

Automated Solution

Postman

const requestedVersion = pm.request.url.path[0];

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

pm.test('Response has API-Version header', () => {
    pm.response.to.have.header('API-Version');
});

pm.test(`API-Version header matches requested version: ${requestedVersion}`, () => {
    const apiVersionHeader = pm.response.headers.get('API-Version');
    pm.expect(apiVersionHeader).to.eql(requestedVersion);
});

This Postman test script extracts the version part from the request URL path (e.g., 'v1' or 'v2').

It then runs three tests:

• Check the response status code is 200 to confirm the request succeeded.
• Verify the response includes the 'API-Version' header to ensure version info is returned.
• Assert that the 'API-Version' header value matches the requested version from the URL, confirming correct versioning.

This approach uses Postman's pm API for clear, readable tests and avoids hardcoding version values inside the test script.

Common Mistakes - 3 Pitfalls

Hardcoding the expected API version inside the test script

{'mistake': "Not checking if the 'API-Version' header exists before asserting its value", 'why_bad': 'If the header is missing, the test will throw an error instead of a clear failure message.', 'correct_approach': 'First assert the header exists, then check its value.'}

Ignoring the response status code and only checking headers

Bonus Challenge

Now add data-driven testing with 3 different API versions: v1, v2, and v3

Show Hint

Practice

1. What is the main purpose of API versioning validation in Postman?

easy

A. To test the API authentication method

B. To check if the API URL is reachable

C. To verify the API response time

D. To ensure the API response uses the correct version

Solution

1. Step 1: Understand API versioning validation

   API versioning validation checks if the API response matches the expected version.

2. Step 2: Identify the main goal in Postman

   In Postman, this means verifying the version value in the response body or headers.

3. Final Answer:

   To ensure the API response uses the correct version -> Option D

4. Quick Check:

   API version check = Correct version [OK]

Hint: Focus on version correctness in API response [OK]

Common Mistakes:

• Confusing version check with response time
• Checking URL reachability instead of version
• Testing authentication instead of version

2. Which Postman test script correctly asserts that the API version in the response header is 'v2'?

easy

A. pm.response.headers.get('api-version').to.eql('v2');

B. pm.expect(pm.response.headers.get('api-version')).to.eql('v2');

C. pm.expect(pm.response.body.apiVersion).to.eql('v2');

D. pm.expect(pm.response.headers['api-version']).to.equal('v2');

Solution

1. Step 1: Check correct method to get header value

   Use pm.response.headers.get('header-name') to get header value in Postman.

2. Step 2: Use pm.expect() with .to.eql() for assertion

   pm.expect(...).to.eql('v2') correctly asserts the value equals 'v2'.

3. Final Answer:

   pm.expect(pm.response.headers.get('api-version')).to.eql('v2'); -> Option B

4. Quick Check:

   Use headers.get() + pm.expect() [OK]

Hint: Use headers.get() with pm.expect().to.eql() for header checks [OK]

Common Mistakes:

• Using pm.response.headers['api-version'] which is undefined
• Calling to.eql() directly on header getter without pm.expect()
• Checking version in body when question asks for header

3. Given this Postman test script, what will be the test result if the response JSON is {"version": "1.0"}?

pm.test('Check API version', () => {
  pm.expect(pm.response.json().version).to.equal('2.0');
});

medium

A. Test throws syntax error

B. Test passes because version key exists

C. Test fails because version is '1.0', not '2.0'

D. Test passes because .to.equal() ignores value

Solution

1. Step 1: Understand the test assertion

   The test expects the version value to be exactly '2.0'.

2. Step 2: Compare actual response version with expected

   The response has version '1.0', which does not equal '2.0', so assertion fails.

3. Final Answer:

   Test fails because version is '1.0', not '2.0' -> Option C

4. Quick Check:

   Expected '2.0' vs actual '1.0' = Fail [OK]

Hint: Match expected version exactly to pass test [OK]

Common Mistakes:

• Assuming test passes if key exists
• Thinking .to.equal() ignores value differences
• Confusing syntax error with assertion failure

4. You wrote this Postman test to check API version in response header:

pm.test('API version is v1', () => {
  pm.expect(pm.response.headers['api-version']).to.eql('v1');
});

But the test always fails. What is the likely issue?

medium

A. pm.response.headers is not an object with keys, use .get() method instead

B. The header name should be capitalized as 'Api-Version'

C. The assertion method should be .to.equal() not .to.eql()

D. pm.expect() cannot be used for header validation

Solution

1. Step 1: Understand how to access headers in Postman

   pm.response.headers is a special object; headers must be accessed with .get('header-name').

2. Step 2: Identify the error in header access

   Using pm.response.headers['api-version'] returns undefined, causing assertion failure.

3. Final Answer:

   pm.response.headers is not an object with keys, use .get() method instead -> Option A

4. Quick Check:

   Use headers.get() to access headers [OK]

Hint: Use headers.get('name') to access headers in Postman [OK]

Common Mistakes:

• Accessing headers like a normal object
• Changing header name case unnecessarily
• Confusing .to.eql() with .to.equal() causing failure

5. You want to validate that your API supports multiple versions: 'v1', 'v2', or 'v3'. Which Postman test script correctly checks the response header 'api-version' against these allowed versions?

hard

A. pm.test('API version is valid', () => {
const version = pm.response.headers.get('api-version');
pm.expect(version).to.be.oneOf(['v1', 'v2', 'v3']);
});

B. pm.test('API version is valid', () => {
const version = pm.response.headers.get('api-version');
pm.expect(version === 'v1' || 'v2' || 'v3').to.be.true;
});

C. pm.test('API version is valid', () => {
const version = pm.response.headers.get('api-version');
pm.expect(version).to.include(['v1', 'v2', 'v3']);
});

D. pm.test('API version is valid', () => {
const version = pm.response.headers.get('api-version');
pm.expect(version).to.eql('v1' || 'v2' || 'v3');
});

Solution

1. Step 1: Understand how to check multiple allowed values

   pm.expect(...).to.be.oneOf(array) checks if value is in the array.

2. Step 2: Analyze each option's correctness

   pm.test('API version is valid', () => { const version = pm.response.headers.get('api-version'); pm.expect(version).to.be.oneOf(['v1', 'v2', 'v3']); }); uses .to.be.oneOf(['v1','v2','v3']) correctly. pm.test('API version is valid', () => { const version = pm.response.headers.get('api-version'); pm.expect(version).to.include(['v1', 'v2', 'v3']); }); uses .to.include(array) which is invalid. pm.test('API version is valid', () => { const version = pm.response.headers.get('api-version'); pm.expect(version === 'v1' || 'v2' || 'v3').to.be.true; }); uses incorrect boolean logic. pm.test('API version is valid', () => { const version = pm.response.headers.get('api-version'); pm.expect(version).to.eql('v1' || 'v2' || 'v3'); }); uses .to.eql() with || which evaluates incorrectly.

3. Final Answer:

   pm.expect(version).to.be.oneOf(['v1', 'v2', 'v3']); -> Option A

4. Quick Check:

   Use .to.be.oneOf() for multiple allowed values [OK]

Hint: Use .to.be.oneOf() to check multiple valid versions [OK]

Common Mistakes:

• Using .to.include() incorrectly on array
• Writing boolean OR logic inside pm.expect()
• Using .to.eql() with OR operator causing wrong check