Response body assertions in Postman - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ assertion

intermediate

Check if response JSON contains a specific key with expected value

Given a JSON response body, which Postman test script correctly asserts that the key status has the value success?

Postman

pm.test('Status is success', function () {
    // Write assertion here
});

A pm.expect(pm.response.json().status).to.eql('success');

B pm.expect(pm.response.json().status).to.be.true();

C pm.expect(pm.response.json().status).to.equal(true);

D pm.expect(pm.response.json().status).to.be('success');

💡 Hint

Use the correct assertion method to compare values exactly.

Option A uses to.eql() which checks deep equality and matches the string 'success'. Other options either use wrong assertion methods or compare to wrong types.

❓ assertion

intermediate

Verify response body contains a non-empty array

Which Postman test script correctly asserts that the response JSON has a key items which is an array with at least one element?

Postman

pm.test('Items array is not empty', function () {
    // Write assertion here
});

A pm.expect(pm.response.json().items).to.be.an('array').that.is.not.empty;

B pm.expect(pm.response.json().items).to.have.lengthOf.above(0);

C pm.expect(pm.response.json().items.length).to.be.above(0);

D pm.expect(pm.response.json().items).to.have.length.above(0);

💡 Hint

Use chaining to check type and emptiness.

Option A correctly asserts that items is an array and is not empty using Chai's BDD style. Other options have syntax errors or incorrect chaining.

❓ Predict Output

advanced

Output of response body assertion with nested JSON

What will be the result of this Postman test script if the response body is {"user":{"id":123,"active":true}}?

Postman

pm.test('User is active', function () {
    pm.expect(pm.response.json().user.active).to.be.false;
});

A Test passes because active is true

B Test fails with assertion error because active is true, not false

C SyntaxError due to incorrect assertion method

D Test fails with TypeError because user key is missing

💡 Hint

Check the actual value of the active key and the assertion used.

The assertion expects active to be false but the response has it as true, so the test fails with an assertion error.

🔧 Debug

advanced

Identify the error in response body assertion script

What is wrong with this Postman test script if the response body is {"data":{"count":5}}?

pm.test('Count is 5', function () {
    pm.expect(pm.response.json().count).to.eql(5);
});

A Test will pass because count equals 5

B SyntaxError due to missing semicolon

C Assertion method to.eql() is invalid

D pm.response.json().count is undefined because count is nested inside data

💡 Hint

Check the JSON path used to access the count key.

The script tries to access count at the root level but it is inside the data object, so pm.response.json().count is undefined causing the assertion to fail.

🧠 Conceptual

expert

Best practice for asserting optional keys in response body

In Postman tests, what is the best way to assert that an optional key message in the response body is either absent or a non-empty string if present?

A Fail the test if <code>message</code> key is missing

B Always assert <code>message</code> is a non-empty string without checking existence

C Use a conditional check: if <code>message</code> exists, assert it is a non-empty string; else pass the test

D Ignore the <code>message</code> key entirely in tests

💡 Hint

Think about how to handle keys that may or may not be present.

Option C is best practice because it handles both cases gracefully: if the key exists, it validates the value; if not, it does not fail the test unnecessarily.