Body validation before sending in Postman - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Why validate request body before sending in Postman?

What is the main reason to validate the request body before sending it in Postman?

A To ensure the server receives data in the expected format and avoid errors

B To automatically generate test reports without running tests

C To speed up the network connection between client and server

D To bypass authentication and send requests faster

💡 Hint

Think about what happens if the server gets wrong or incomplete data.

Validating the request body helps catch mistakes early, so the server can process the data correctly and avoid errors.

❓ Predict Output

intermediate

What is the output of this Postman test script?

Given this Postman test script that validates a JSON body field, what will be the test result?

Postman

pm.test('Check user ID is number', () => {
  const jsonData = pm.request.body.raw ? JSON.parse(pm.request.body.raw) : {};
  pm.expect(typeof jsonData.userId).to.eql('number');
});

A Test fails if userId is a number in the request body

B Test passes if userId is a number in the request body

C Test passes regardless of userId type

D Test throws a syntax error

💡 Hint

Look at the type check and what pm.expect compares.

The test checks if the userId field in the JSON body is a number. If yes, the test passes; otherwise, it fails.

❓ assertion

advanced

Which assertion correctly validates a non-empty string field in Postman?

Choose the assertion that correctly checks if the 'username' field in the JSON body is a non-empty string.

Postman

const jsonData = pm.request.body.raw ? JSON.parse(pm.request.body.raw) : {};

A pm.expect(jsonData.username).to.exist.and.to.be.empty;

B pm.expect(jsonData.username).to.be.a('number').and.not.empty;

C pm.expect(jsonData.username).to.be.a('string').and.not.empty;

D pm.expect(jsonData.username).to.be.undefined;

💡 Hint

Check the data type and if the string is empty or not.

Option C correctly asserts that username is a string and not empty. Other options check wrong types or wrong conditions.

🔧 Debug

advanced

Why does this Postman test script fail with SyntaxError?

Identify the cause of the SyntaxError in this Postman test script:

Postman

pm.test('Validate JSON body', () => {
  const data = JSON.parse(pm.request.body.raw);
  pm.expect(data.email).to.match(/^[^@\s]+@[^@\s]+\.[^@\s]+$/);
});

A The regex pattern is missing proper escaping for backslashes

B The test function is missing a closing brace

C pm.expect is used incorrectly without parentheses

D pm.request.body.raw is undefined causing JSON.parse to fail

💡 Hint

Check if pm.request.body.raw always contains a string before parsing.

If pm.request.body.raw is undefined or empty, JSON.parse throws a SyntaxError because it expects a valid JSON string.

❓ framework

expert

How to implement conditional body validation in Postman pre-request script?

You want to validate the request body only if the HTTP method is POST. Which pre-request script correctly implements this conditional validation?

A

if (pm.request.method === 'POST') {
  const body = JSON.parse(pm.request.body.raw);
  if (!body.name) throw new Error('Name is required');
}

B

if (pm.request.method = 'POST') {
  const body = JSON.parse(pm.request.body.raw);
  if (!body.name) throw new Error('Name is required');
}

C

if (pm.request.method === 'post') {
  const body = JSON.parse(pm.request.body.raw);
  if (!body.name) throw new Error('Name is required');
}

D

if (pm.request.method !== 'POST') {
  const body = JSON.parse(pm.request.body.raw);
  if (!body.name) throw new Error('Name is required');
}

💡 Hint

Check the equality operator and case sensitivity of HTTP methods.

Option A correctly uses strict equality (===) and uppercase 'POST' to conditionally validate the body only for POST requests.