Header assertions in Postman - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ assertion

intermediate

Check for exact header value

You want to verify that the response header Content-Type exactly equals application/json; charset=utf-8. Which Postman test snippet correctly asserts this?

A pm.test('Content-Type is correct', () => { pm.response.to.have.header('content-type', 'application/json'); });

B pm.test('Content-Type is correct', () => { pm.response.headers.get('Content-Type') === 'application/json; charset=utf-8'; });

C pm.test('Content-Type is correct', () => { pm.expect(pm.response.headers['Content-Type']).to.equal('application/json; charset=utf-8'); });

D pm.test('Content-Type is correct', () => { pm.response.to.have.header('Content-Type', 'application/json; charset=utf-8'); });

💡 Hint

Use Postman's built-in assertion methods for headers.

Option D uses pm.response.to.have.header(name, value) which checks the header name and exact value.

Option D only compares but does not assert, so test will not fail on mismatch.

Option D tries to access headers as an object, but pm.response.headers is not a plain object.

Option D checks a different value and header name case sensitivity matters in assertion methods.

❓ assertion

intermediate

Verify header presence without value check

Which Postman test code correctly asserts that the response contains a header named X-Request-ID, regardless of its value?

A pm.test('X-Request-ID header exists', () => { pm.response.to.have.header('X-Request-ID'); });

B pm.test('X-Request-ID header exists', () => { pm.expect(pm.response.headers.get('X-Request-ID')).to.exist; });

C pm.test('X-Request-ID header exists', () => { pm.response.headers.has('X-Request-ID'); });

D pm.test('X-Request-ID header exists', () => { pm.expect(pm.response.headers['X-Request-ID']).to.be.ok; });

💡 Hint

Use Postman's header assertion method that checks presence only.

Option A uses pm.response.to.have.header(name) which asserts header presence.

Option A uses pm.expect(...).to.exist but pm.response.headers.get() returns null if missing, so this works but is less direct.

Option A calls has() but does not assert, so test won't fail if header missing.

Option A tries to access headers as object, which is invalid.

❓ Predict Output

advanced

Output of header value assertion with regex

What will be the result of this Postman test if the response header Server is nginx/1.18.0?

Postman

pm.test('Server header matches nginx version', () => {
  pm.expect(pm.response.headers.get('Server')).to.match(/^nginx\/\d+\.\d+\.\d+$/);
});

A Test fails due to syntax error in regex.

B Test passes because header matches regex exactly.

C Test fails because regex expects three version numbers but header has only two.

D Test passes because regex matches any string starting with 'nginx'.

💡 Hint

Check the regex pattern and the actual header value carefully.

The regex expects three numbers separated by dots (e.g., 1.18.0), but the header is 'nginx/1.18.0' which has only two dots, so it does not match the pattern expecting three numbers.

Therefore, the test fails.

🔧 Debug

advanced

Identify the error in header assertion code

This Postman test is intended to check that the Cache-Control header contains the word no-cache. What is wrong with it?

Postman

pm.test('Cache-Control contains no-cache', () => {
  pm.expect(pm.response.headers.get('Cache-Control')).to.include('no-cache');
});

A The method 'to.include' does not exist; it should be 'to.contain'.

B If the header is missing, 'get' returns null and 'to.include' causes an error.

C The header name should be lowercase 'cache-control' to match.

D The assertion should use 'pm.response.to.have.header' instead.

💡 Hint

Consider what happens if the header is not present.

If the header Cache-Control is missing, pm.response.headers.get() returns null.

Calling to.include on null causes a runtime error.

To fix, check header presence before asserting content or handle null safely.

🧠 Conceptual

expert

Best practice for asserting multiple headers in Postman

You want to assert that the response contains headers Content-Type with value application/json and Cache-Control with value no-store. Which approach is best to ensure clear, maintainable tests?

A Write separate tests for each header: pm.test('Content-Type check', () => { pm.response.to.have.header('Content-Type', 'application/json'); }); pm.test('Cache-Control check', () => { pm.response.to.have.header('Cache-Control', 'no-store'); });

B Use a single assertion with a custom function to check both headers at once.

C Write one test with multiple assertions inside: pm.test('Headers check', () => { pm.response.to.have.header('Content-Type', 'application/json'); pm.response.to.have.header('Cache-Control', 'no-store'); });

D Combine headers into one string and assert: pm.test('Headers combined', () => { pm.expect(pm.response.headers.toString()).to.include('Content-Type: application/json').and.to.include('Cache-Control: no-store'); });

💡 Hint

Think about test clarity and reporting.

Option A is best because separate tests give clear, isolated results for each header.

Option A works but bundles multiple checks, making it harder to identify which header failed.

Option A is fragile and depends on string formatting.

Option A adds unnecessary complexity.