Variable assignment in flows in Postman - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Variable assignment in Postman pre-request script

What will be the value of the environment variable token after running this pre-request script in Postman?

Postman

pm.environment.set('token', 'initial');
if (pm.response && pm.response.code === 200) {
  pm.environment.set('token', 'updated');
} else {
  pm.environment.set('token', 'failed');
}

A "failed"

B "initial"

C "updated"

D undefined

💡 Hint

Remember that pre-request scripts run before the request is sent, so pm.response is not yet available.

In a pre-request script, pm.response is undefined because the request has not been sent yet. Therefore, the if condition is false, and the variable token is set to "failed".

❓ assertion

intermediate

Correct assertion for variable assignment in Postman test script

Which assertion correctly verifies that the global variable userId has been assigned the value 12345 in a Postman test script?

A pm.test('userId is 12345', () => pm.globals.get('userId') === '12345');

B pm.test('userId is 12345', () => pm.expect(pm.globals.get('userId')).to.eql('12345'));

C pm.test('userId is 12345', () => pm.globals.userId === 12345);

D pm.test('userId is 12345', () => pm.expect(pm.globals.userId).to.equal(12345));

💡 Hint

Use pm.expect with pm.globals.get() to access global variables properly.

Option B uses pm.expect to assert that the global variable userId (accessed via pm.globals.get('userId')) equals the string '12345'. This is the correct way to assert variable values in Postman test scripts.

🔧 Debug

advanced

Debugging variable assignment in Postman flow

Given this Postman test script, why does the variable sessionId remain undefined after the request?

Postman

if (pm.response.code === 200) {
  pm.variables.set('sessionId', pm.response.json().session);
}
console.log(pm.variables.get('sessionId'));

A Because <code>pm.variables.set</code> requires a third argument to persist the variable.

B Because <code>pm.response.code</code> is undefined in test scripts.

C Because <code>pm.response.json()</code> is not a valid method to parse JSON response.

D Because <code>pm.variables</code> only stores variables for the current request and is not persisted between requests.

💡 Hint

Consider the scope and lifetime of pm.variables compared to environment or global variables.

pm.variables stores variables only for the current request execution and does not persist them between requests. To keep sessionId for later requests, use pm.environment.set or pm.globals.set.

🧠 Conceptual

advanced

Understanding variable scopes in Postman flows

Which statement correctly describes the difference between pm.variables, pm.environment, and pm.globals in Postman?

A <code>pm.variables</code> are temporary for the current request, <code>pm.environment</code> variables persist per environment, and <code>pm.globals</code> persist globally across all environments.

B <code>pm.variables</code> persist globally, <code>pm.environment</code> are temporary, and <code>pm.globals</code> persist per environment.

C <code>pm.variables</code> and <code>pm.environment</code> are the same, but <code>pm.globals</code> are temporary.

D <code>pm.variables</code> persist per environment, <code>pm.environment</code> persist globally, and <code>pm.globals</code> are temporary.

💡 Hint

Think about how long each variable type lasts and where it is accessible.

pm.variables exist only during the current request execution and are not saved. pm.environment variables are saved per environment and persist across requests. pm.globals variables are saved globally and accessible in all environments.

❓ framework

expert

Postman flow variable assignment and test execution order

In a Postman collection run, which sequence correctly describes when variables are assigned and accessible during the flow?

A Variables set in pre-request scripts are only available after the entire collection run finishes; test scripts run before pre-request scripts.

B Test scripts run before the request; then pre-request scripts run; then the request is sent; variables set in test scripts are not saved.

C Pre-request scripts run first and can set variables; then the request is sent; then test scripts run and can update variables; environment and global variables persist between requests.

D Requests run first; then pre-request scripts run; then test scripts run; variables set in pre-request scripts are not accessible in test scripts.

💡 Hint

Recall the order of execution in Postman: pre-request script, request, test script.

Postman executes pre-request scripts before sending the request, allowing variable assignment before the request. After the request, test scripts run and can update variables. Environment and global variables persist between requests and across the collection run.

Practice

1. What does pm.variables.set('token', 'abc123') do in a Postman test script?

easy

A. It saves the value 'abc123' to a variable named 'token' for later use.

B. It retrieves the value of the variable 'token'.

C. It deletes the variable named 'token'.

D. It sends 'abc123' as a request header named 'token'.

Solution

1. Step 1: Understand the method pm.variables.set

   This method assigns a value to a variable in Postman scripts.

2. Step 2: Analyze the parameters

   The first parameter is the variable name 'token', the second is the value 'abc123' to store.

3. Final Answer:

   It saves the value 'abc123' to a variable named 'token' for later use. -> Option A

4. Quick Check:

   pm.variables.set saves data [OK]

Hint: Set stores data; get retrieves it [OK]

Common Mistakes:

• Confusing set with get method
• Thinking set deletes variables
• Assuming set sends data in requests

2. Which of the following is the correct syntax to assign a variable named 'userId' with value 42 in a Postman test script?

easy

A. pm.variables.get('userId', 42);

B. pm.variables.store('userId', 42);

C. pm.variables.assign('userId' = 42);

D. pm.variables.set('userId', 42);

Solution

1. Step 1: Recall the correct method for assigning variables

   The method to assign a variable is pm.variables.set(name, value).

2. Step 2: Check each option's syntax

   pm.variables.set('userId', 42); uses pm.variables.set('userId', 42); which is correct syntax.

3. Final Answer:

   pm.variables.set('userId', 42); -> Option D

4. Quick Check:

   Use pm.variables.set to assign [OK]

Hint: Set method assigns variables with (name, value) [OK]

Common Mistakes:

• Using get instead of set to assign
• Incorrect method names like assign or store
• Wrong parameter syntax with equals sign

3. Consider this Postman test script snippet:

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. 5

B. 8

C. Error

D. undefined

Solution

1. Step 1: Analyze the first assignment

   The variable 'count' is set to 5 initially.

2. Step 2: Analyze the second assignment

   It gets the current 'count' value (5), adds 3, and sets 'count' to 8.

3. Step 3: Check the console.log output

   It prints the updated value of 'count', which is 8.

4. Final Answer:

   8 -> Option B

5. Quick Check:

   5 + 3 = 8 [OK]

Hint: Get current value, add, then set updated value [OK]

Common Mistakes:

• Assuming the first value stays unchanged
• Thinking get returns undefined
• Confusing set and get usage

4. You wrote this Postman test script:

pm.variables.set('status', 'active')
pm.variables.get('status')

But the test fails because the variable 'status' is undefined. What is the likely cause?

medium

A. Variables set in one request are not available in another without environment or global scope.

B. pm.variables.get returns undefined if set is not awaited.

C. Missing semicolon after set statement causes failure.

D. Variable names cannot be strings.

Solution

1. Step 1: Understand variable scopes in Postman

   Variables set with pm.variables.set are local to the current request script and do not persist across requests.

2. Step 2: Identify why 'status' is undefined

   If you try to get 'status' in a different request without using environment or global variables, it will be undefined.

3. Final Answer:

   Variables set in one request are not available in another without environment or global scope. -> Option A

4. Quick Check:

   Local variables don't persist across requests [OK]

Hint: Use environment/global variables for cross-request data [OK]

Common Mistakes:

• Thinking semicolons affect variable persistence
• Believing get waits for set automatically
• Assuming variable names can't be strings

5. You want to save a user token from a response JSON and reuse it in the next request. Which flow correctly assigns and retrieves the token using Postman variables?

hard

A. In first request test script: pm.variables.set('token', pm.response.json().token);In next request pre-request script: const token = pm.environment.get('token');

B. In first request test script: pm.variables.set('token', pm.response.json().token);In next request pre-request script: const token = pm.variables.get('token');

C. In first request test script: pm.environment.set('token', pm.response.json().token);In next request pre-request script: const token = pm.environment.get('token');

D. In first request test script: pm.environment.set('token', pm.response.json().token);In next request pre-request script: const token = pm.variables.get('token');

Solution

1. Step 1: Identify variable scope for cross-request use

   To reuse data across requests, environment variables must be used, not local variables.

2. Step 2: Match correct set and get methods

   In first request test script: pm.environment.set('token', pm.response.json().token);
   In next request pre-request script: const token = pm.environment.get('token'); uses pm.environment.set and pm.environment.get, which correctly share data between requests.

3. Final Answer:

   Use environment variables to save and retrieve token across requests. -> Option C

4. Quick Check:

   Environment variables persist across requests [OK]

Hint: Use environment variables for data between requests [OK]

Common Mistakes:

• Using pm.variables for cross-request data
• Mixing environment and local variable methods
• Not retrieving variables in the correct scope