Response body inspection in Postman - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this Postman test script?

Given the following Postman test script that inspects the response body, what will be the test result?

Postman

pm.test("Check user name", function () {
    var jsonData = pm.response.json();
    pm.expect(jsonData.user.name).to.eql("Alice");
});

A Test fails if response JSON is not a JSON object

B Test fails if response JSON has user.name exactly 'Alice'

C Test passes if response JSON has user.name containing 'Alice' anywhere

D Test passes if response JSON has user.name exactly 'Alice'

💡 Hint

Look at the assertion method to.eql and what it checks.

The test uses pm.expect(...).to.eql(...) which checks for exact equality. The test passes only if jsonData.user.name is exactly 'Alice'.

❓ assertion

intermediate

Which assertion correctly checks if response body contains a key 'status' with value 'success'?

Choose the Postman test assertion that correctly verifies the response body JSON has a key status with value success.

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

B pm.expect(pm.response.body.status).to.eql('success');

C pm.expect(pm.response.json().status).to.contain('success');

D pm.expect(pm.response.body).to.have.property('status', 'success');

💡 Hint

Remember that pm.response.json() parses the response body as JSON.

Option A correctly parses the response body as JSON and asserts the status key equals 'success'. Option A is invalid because pm.response.body is a string, not an object. Option A uses to.contain which is for strings or arrays, not exact equality. Option A is invalid because pm.response.body is a string and does not have have.property.

🔧 Debug

advanced

Why does this Postman test fail with 'TypeError: Cannot read property "id" of undefined'?

Consider this test script:

pm.test("Check user id", function () {
    var jsonData = pm.response.json();
    pm.expect(jsonData.user.id).to.be.a('number');
});

The test fails with the error above. What is the most likely cause?

A The 'id' property exists but is not a number, causing the assertion to fail.

B The response body is not valid JSON, so pm.response.json() throws an error.

C The response JSON does not have a 'user' key, so jsonData.user is undefined.

D The test script syntax is incorrect and causes a runtime error.

💡 Hint

Check what happens if you try to access a property of undefined.

The error means jsonData.user is undefined, so trying to access id on it causes a TypeError. This happens if the response JSON lacks the 'user' key.

🧠 Conceptual

advanced

What is the best way to check if a response body contains an array with at least one item?

In Postman, you want to verify the response body JSON has an array called items and it contains at least one element. Which test assertion is correct?

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

B pm.expect(pm.response.json().items).to.be.an('array').and.to.have.length.above(0);

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

D pm.expect(pm.response.json().items).to.be.an('array').with.length.above(0);

💡 Hint

Check how to assert type and length in Postman using Chai assertions.

Option B correctly asserts that items is an array and its length is greater than 0. Option B only checks length but not type. Option B uses incorrect chaining. Option B uses invalid chaining syntax.

❓ framework

expert

How to write a Postman test to verify nested JSON keys safely?

You want to write a Postman test that checks if response.data.user.profile.email exists and is a non-empty string, but the response may not always have all nested keys. Which approach is safest to avoid runtime errors?

A var jsonData = pm.response.json(); pm.expect(jsonData.data && jsonData.data.user && jsonData.data.user.profile && jsonData.data.user.profile.email).to.be.a('string').and.not.empty;

B pm.expect(pm.response.json()?.data?.user?.profile?.email).to.be.a('string').and.not.empty;

C pm.expect(pm.response.json().data.user.profile.email).to.be.a('string').and.not.empty;

D var email = pm.response.json().data.user.profile.email || ''; pm.expect(email).to.be.a('string').and.not.empty;

💡 Hint

Think about how to safely access nested properties without causing errors.

Option A uses explicit checks for each nested key before accessing email, preventing runtime errors if any key is missing. Option A will throw an error if any key is missing. Option A uses optional chaining which is not supported in Postman test scripts. Option A assumes email exists and uses fallback but will throw if intermediate keys are missing.