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.

Practice

1. What is the main purpose of local variables in Postman?

easy

A. To create global environment settings

B. To save data permanently across all requests

C. To share data between different collections

D. To store data only during a single request execution

Solution

1. Step 1: Understand local variable scope

   Local variables exist only during the execution of one request and are not saved beyond that.

2. Step 2: Compare with other variable types

   Global or environment variables persist beyond one request, unlike local variables.

3. Final Answer:

   To store data only during a single request execution -> Option D

4. Quick Check:

   Local variables = single request scope [OK]

Hint: Local variables last only during one request [OK]

Common Mistakes:

• Confusing local variables with global variables
• Thinking local variables persist across requests
• Assuming local variables share data between collections

2. Which of the following is the correct syntax to set a local variable named token with value abc123 in Postman?

easy

A. pm.local.set('token', 'abc123');

B. pm.environment.set('token', 'abc123');

C. pm.variables.set('token', 'abc123');

D. pm.globals.set('token', 'abc123');

Solution

1. Step 1: Identify the correct method for local variables

   Local variables use pm.variables.set to assign values.

2. Step 2: Check other options for correctness

   pm.environment.set and pm.globals.set set environment and global variables, not local. pm.local.set is invalid.

3. Final Answer:

   pm.variables.set('token', 'abc123'); -> Option C

4. Quick Check:

   Set local variable = pm.variables.set [OK]

Hint: Use pm.variables.set() for local variables [OK]

Common Mistakes:

• Using pm.environment.set instead of pm.variables.set
• Trying to use pm.local.set which does not exist
• Confusing global and local variable methods

3. Consider this Postman test script:

pm.variables.set('count', 5);
pm.variables.set('count', pm.variables.get('count') + 3);
console.log(pm.variables.get('count'));

What will be printed in the console?

medium

A. 8

B. 5

C. Error: Cannot add number to undefined

D. null

Solution

1. Step 1: Set initial local variable 'count'

   The first line sets 'count' to 5.

2. Step 2: Increment 'count' by 3

   The second line gets 'count' (5), adds 3, and sets it back to 8.

3. Step 3: Output the updated value

   The console.log prints the current value of 'count', which is 8.

4. Final Answer:

   8 -> Option A

5. Quick Check:

   5 + 3 = 8 [OK]

Hint: Get then set to update local variable value [OK]

Common Mistakes:

• Assuming the variable does not update
• Expecting an error due to type mismatch
• Confusing local with environment variables

4. You wrote this Postman script:

pm.variables.set('user', 'Alice');
console.log(pm.variables.get('username'));

What is the problem here?

medium

A. Variable 'username' was never set, so get returns undefined

B. Syntax error in pm.variables.set method

C. Local variables cannot be logged to console

D. pm.variables.get requires two arguments

Solution

1. Step 1: Check variable names used

   The script sets 'user' but tries to get 'username', which was never set.

2. Step 2: Understand get behavior for unset variables

   Getting an unset local variable returns undefined, no error occurs.

3. Final Answer:

   Variable 'username' was never set, so get returns undefined -> Option A

4. Quick Check:

   Unset variable get = undefined [OK]

Hint: Check variable names carefully for typos [OK]

Common Mistakes:

• Assuming syntax error when variable name mismatches
• Thinking pm.variables.get needs two arguments
• Believing console.log cannot show local variables

5. You want to store a temporary token during a request and use it in multiple tests within that request. Which approach correctly uses local variables to achieve this?

hard

A. Set the token with pm.environment.set('token', 'abc') and get it with pm.variables.get('token')

B. Set the token once with pm.variables.set('token', 'abc') and get it in tests with pm.variables.get('token')

C. Set the token with pm.variables.set('token', 'abc') but cannot access it in other tests

D. Set the token with pm.globals.set('token', 'abc') and get it with pm.variables.get('token')

Solution

1. Step 1: Understand local variable scope within one request

   Local variables set with pm.variables.set are accessible throughout the request execution, including multiple tests.

2. Step 2: Verify correct get method usage

   Use pm.variables.get to retrieve the local variable value within the same request.

3. Step 3: Check other options for scope mismatch

   Environment and global variables persist beyond one request and are not local. Also, local variables are accessible across tests in the same request.

4. Final Answer:

   Set the token once with pm.variables.set('token', 'abc') and get it in tests with pm.variables.get('token') -> Option B

5. Quick Check:

   Local variable set/get works within one request [OK]

Hint: Use pm.variables.set/get to share data within one request [OK]

Common Mistakes:

• Using environment or global variables instead of local
• Thinking local variables cannot be shared between tests in one request
• Mixing set and get methods from different scopes