Variable syntax ({{variable}}) 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, what will be the value of responseVar after execution?

pm.variables.set("userId", 123);
const responseVar = pm.variables.get("userId");

Postman

pm.variables.set("userId", 123);
const responseVar = pm.variables.get("userId");

A null

B "userId"

C undefined

D 123

💡 Hint

Remember that pm.variables.set stores a variable and pm.variables.get retrieves its value.

The variable userId is set to the number 123, so retrieving it returns 123.

❓ assertion

intermediate

Which assertion correctly checks if a variable {{token}} is not empty?

In a Postman test script, you want to assert that the variable {{token}} is not an empty string. Which assertion is correct?

A pm.expect(pm.variables.get('token')).to.not.be.empty;

B pm.expect(pm.variables.get('token')).to.equal('');

C pm.expect(pm.variables.get('token')).to.be.undefined;

D pm.expect(pm.variables.get('token')).to.be.null;

💡 Hint

Think about how to check that a string is not empty using Postman assertions.

Option A correctly asserts that the variable is not empty. Options A, C, and D check for empty, undefined, or null, which are not what we want.

❓ locator

advanced

Which variable syntax correctly accesses an environment variable named 'sessionId' in Postman?

In Postman, you want to access the environment variable sessionId inside a test script. Which syntax is correct?

A pm.environment.get('sessionId')

B pm.variables.get('sessionId')

C {{sessionId}}

D pm.globals.get('sessionId')

💡 Hint

Remember that environment variables are accessed differently than local or global variables.

Option A uses pm.environment.get which is the correct way to get environment variables. Option A is a template syntax not usable directly in scripts, Option A gets local variables, and D accesses global variables.

🔧 Debug

advanced

Why does this Postman script fail to replace {{user}} in the request URL?

Consider this Postman request URL: https://api.example.com/users/{{user}}. The variable user is set in the collection variables. The test script contains:

pm.variables.set('user', 'alice');

Why does the URL not replace {{user}} with 'alice' when the request runs?

A Because collection variables override local variables, so the URL uses the collection variable value.

B Because the variable name 'user' is reserved and cannot be used.

C Because pm.variables.set sets a local variable that does not affect URL variable substitution.

D Because variable substitution only works with environment variables, not collection variables.

💡 Hint

Think about when variable substitution happens in Postman and which variable scopes affect it.

pm.variables.set sets a local variable for the script runtime but does not change the variable used in the URL before the request is sent. URL substitution uses environment, collection, or global variables, not local script variables.

❓ framework

expert

In Postman, which variable scope has the highest priority during variable substitution?

Postman supports multiple variable scopes: global, environment, collection, and local (script). When Postman replaces variables like {{varName}} in a request, which scope does it check first?

A Collection variables

B Local (script) variables

C Environment variables

D Global variables

💡 Hint

Consider the order Postman uses to resolve variables for substitution in requests.

Postman resolves variables for substitution in this order (highest to lowest priority): local (script) variables, collection variables, environment variables, then global variables. Local variables set using pm.variables.set() in pre-request scripts do affect request variable substitution.

Practice

1. What is the correct way to use a variable named userId in a Postman request URL?

easy

A. Use $userId in the URL to insert the variable value.

B. Use [userId] in the URL to insert the variable value.

C. Use {{userId}} in the URL to insert the variable value.

D. Use userId directly without any special syntax.

Solution

1. Step 1: Understand Postman variable syntax

   Postman uses double curly braces {{variable}} to insert variable values dynamically.

2. Step 2: Apply syntax to the variable userId

   To use the variable userId, you write {{userId}} in the request URL or body.

3. Final Answer:

   Use {{userId}} in the URL to insert the variable value. -> Option C

4. Quick Check:

   Variable syntax = {{variable}} [OK]

Hint: Remember variables always use double curly braces {{}} [OK]

Common Mistakes:

• Using single brackets or dollar sign instead of {{}}
• Writing variable name without any braces
• Confusing variable syntax with other languages

2. Which of the following is the correct syntax to reference a variable named token in Postman?

easy

A. {token}

B. {{token}}

C. [[token]]

D. $token

Solution

1. Step 1: Recall Postman variable syntax rules

   Postman requires variables to be wrapped in double curly braces to be recognized.

2. Step 2: Match the correct syntax for variable token

   The correct syntax is {{token}}, which tells Postman to replace it with the variable's value.

3. Final Answer:

   {{token}} -> Option B

4. Quick Check:

   Variable reference = {{variable}} [OK]

Hint: Always use double curly braces {{}} for variables [OK]

Common Mistakes:

• Using single braces or brackets
• Using dollar sign prefix
• Forgetting braces entirely

3. Given the environment variable baseUrl is set to https://api.example.com, what will be the full URL when the request uses {{baseUrl}}/users?

medium

A. https://api.example.comusers

B. {{baseUrl}}/users

C. https://api.example.com{{baseUrl}}/users

D. https://api.example.com/users

Solution

1. Step 1: Understand variable substitution in Postman

   Postman replaces {{baseUrl}} with its set value before sending the request.

2. Step 2: Substitute {{baseUrl}} with its value

   Since baseUrl is https://api.example.com, the URL becomes https://api.example.com/users.

3. Final Answer:

   https://api.example.com/users -> Option D

4. Quick Check:

   Variable replaced URL = https://api.example.com/users [OK]

Hint: Variables replace exactly with their set values [OK]

Common Mistakes:

• Not replacing variable and leaving {{baseUrl}} as is
• Concatenating variable value incorrectly
• Missing slash between baseUrl and path

4. You wrote Authorization: Bearer {token} in the headers, but the token is not replaced. What is the error?

medium

A. Variable syntax is incorrect; should be {{token}}.

B. Token variable is not set anywhere.

C. Bearer keyword is missing.

D. Headers do not support variables.

Solution

1. Step 1: Check the variable syntax in the header

   The header uses {token} which is missing one pair of curly braces.

2. Step 2: Correct the syntax to {{token}}

   Postman requires double curly braces to recognize variables, so it should be Authorization: Bearer {{token}}.

3. Final Answer:

   Variable syntax is incorrect; should be {{token}}. -> Option A

4. Quick Check:

   Correct variable syntax = {{variable}} [OK]

Hint: Always use double curly braces {{}} for variables in headers too [OK]

Common Mistakes:

• Using single braces instead of double
• Assuming variables auto-replace without braces
• Not setting the variable value before use

5. You want to reuse a variable sessionId inside a JSON body and a header in Postman. Which is the best practice to ensure it works correctly?

hard

A. Set sessionId as an environment variable and use {{sessionId}} in both places.

B. Write sessionId value directly in JSON and header without variables.

C. Use different variable syntaxes in JSON and header for safety.

D. Set sessionId only in the header; JSON will inherit it automatically.

Solution

1. Step 1: Understand variable scope and reuse in Postman

   Environment variables are accessible throughout the request, including headers and body.

2. Step 2: Use consistent variable syntax {{sessionId}} in both JSON body and header

   This ensures Postman replaces the variable correctly wherever it appears.

3. Final Answer:

   Set sessionId as an environment variable and use {{sessionId}} in both places. -> Option A

4. Quick Check:

   Use environment variables + {{variable}} syntax for reuse [OK]

Hint: Set once as environment variable, use {{variable}} everywhere [OK]

Common Mistakes:

• Hardcoding values instead of variables
• Using inconsistent variable syntax
• Assuming variables auto-share without setting scope