Local variables in Postman - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this Postman test script?

Consider the following Postman test script that uses local variables. What will be the value of the variable result after execution?

Postman

pm.test("Check local variable scope", function () {
    let result = 0;
    if (true) {
        let result = 5;
    }
    pm.expect(result).to.eql(0);
});

A Test passes because <code>result</code> is 5

B Test fails because <code>result</code> is 5

C Test fails with ReferenceError because <code>result</code> is undefined

D Test passes because <code>result</code> is 0

💡 Hint

Remember that let declares block-scoped variables.

The variable result declared inside the if block is a different local variable than the one outside. The outer result remains 0, so the test passes.

❓ assertion

intermediate

Which assertion correctly tests a local variable in Postman?

You have a local variable statusCode set to pm.response.code. Which assertion correctly verifies it equals 200?

A pm.expect(statusCode).to.equal(200);

B pm.expect(statusCode).to.be(200);

C pm.expect(statusCode == 200).to.be.true;

D pm.expect(pm.response.code).to.eql('200');

💡 Hint

Use the correct Chai assertion syntax for equality.

Option A uses to.equal(200) which correctly asserts the numeric value. Option A compares number to string, causing failure. Option A uses a boolean expression inside expect, which is less clear. Option A uses invalid syntax.

🔧 Debug

advanced

Why does this Postman script fail to update the local variable?

Given this script, why does the count variable not increment as expected?

let count = 0;
pm.test('Increment count', () => {
  let count = count + 1;
  pm.expect(count).to.eql(1);
});

A The assertion is incorrect; it should check for 0 instead of 1

B The variable <code>count</code> is immutable and cannot be incremented

C The inner <code>let count</code> shadows the outer variable, causing a ReferenceError on right side

D The test passes because <code>count</code> is incremented correctly

💡 Hint

Consider variable shadowing and initialization order.

The inner let count tries to initialize itself with count + 1, but this count refers to itself (not the outer one), causing a ReferenceError.

🧠 Conceptual

advanced

What is the scope of local variables declared with let inside Postman test scripts?

Choose the best description of the scope of a variable declared with let inside a Postman test script function.

A The variable is scoped only within the block or function where it is declared

B The variable is globally accessible throughout all requests and tests

C The variable is accessible only within the Postman environment variables

D The variable is accessible across all collections and environments automatically

💡 Hint

Think about JavaScript block scoping rules.

Variables declared with let are block-scoped, meaning they exist only inside the block or function where declared. They are not global or shared across requests.

❓ framework

expert

How to correctly use local variables to share data between multiple Postman tests in the same request?

You want to share a local variable token between multiple pm.test blocks in the same Postman request script. Which approach works best?

A Declare <code>let token</code> inside each <code>pm.test</code> block separately

B Declare <code>let token = pm.response.json().token;</code> once outside all <code>pm.test</code> blocks, then use <code>token</code> inside each test

C Use <code>pm.variables.set('token', ...)</code> to set a global variable accessible in all tests

D Declare <code>var token</code> inside the first <code>pm.test</code> block and access it in others

💡 Hint

Local variables declared outside test blocks can be shared inside them.

Declaring token once outside all pm.test blocks makes it accessible inside each test because they share the same function scope. Declaring inside each test creates separate variables. Using pm.variables.set sets environment or collection variables, not local variables. Using var inside a block does not guarantee sharing across tests.