Extracting data from responses in Postman - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the purpose of extracting data from responses in Postman?

Extracting data from responses allows you to save values from one API call and use them in subsequent requests, enabling dynamic and chained testing.

beginner

Which Postman feature is commonly used to extract data from a JSON response?

The pm.response.json() function is used to parse the JSON response body so you can access its properties and extract data.

intermediate

How do you save an extracted value as an environment variable in Postman?

Use pm.environment.set('variableName', value); inside the Tests tab to save the extracted value for use in other requests.

intermediate

Example: Extract the user ID from this JSON response:

{"user": {"id": 123, "name": "Alice"}}

Use <code>let jsonData = pm.response.json(); pm.environment.set('userId', jsonData.user.id);</code> to save the user ID as an environment variable.

beginner

Why is it important to check the response status before extracting data?

Checking the response status ensures the request was successful (e.g., status 200) before trying to extract data, preventing errors from invalid or empty responses.

Which Postman method parses the response body as JSON?

A pm.request.body()

B pm.response.text()

C pm.response.json()

D pm.environment.get()

pm.response.json() parses the response body as JSON so you can access its properties.

How do you save a value to an environment variable in Postman?

A pm.environment.set('varName', value);

B pm.response.set('varName', value);

C pm.request.set('varName', value);

D pm.variables.save('varName', value);

pm.environment.set('varName', value); saves a value to an environment variable.

Why should you check the response status before extracting data?

A To speed up the test execution

B To clear environment variables

C To change the request method

D To ensure the response is successful and data is valid

Checking status confirms the response is successful before extracting data.

What type of data can you extract from a Postman response?

A Only images

B JSON, XML, HTML, or plain text

C Only XML

D Only JSON

Postman can extract data from various response formats including JSON, XML, HTML, and plain text.

Which tab in Postman do you write scripts to extract data from responses?

A Tests

B Pre-request Script

C Body

D Headers

The Tests tab is where you write scripts to extract data after receiving the response.

Explain how to extract a value from a JSON response and save it as an environment variable in Postman.

Think about parsing JSON and saving variables for later use.

Why is it important to validate the response status before extracting data in Postman tests?

Consider what happens if the response is an error.

Practice

1. What is the primary purpose of extracting data from API responses in Postman?

easy

A. To reuse data in subsequent API requests

B. To change the API endpoint URL

C. To modify the request headers

D. To delete the response data

Solution

1. Step 1: Understand the role of data extraction

   Extracting data allows you to capture values from one response to use later.

2. Step 2: Connect API requests using extracted data

   This helps chain requests by passing data like tokens or IDs forward.

3. Final Answer:

   To reuse data in subsequent API requests -> Option A

4. Quick Check:

   Extract data = reuse in next requests [OK]

Hint: Extract data to pass info between requests [OK]

Common Mistakes:

• Thinking extraction changes the URL
• Confusing extraction with header modification
• Believing extraction deletes data

2. Which Postman script correctly extracts the value of userId from a JSON response and saves it as an environment variable?

easy

A. let data = pm.response.json(); pm.environment.set('userId', data.userId);

B. pm.response.set('userId', pm.response.json().userId);

C. pm.environment.get('userId', pm.response.json().userId);

D. let userId = pm.response.set('userId');

Solution

1. Step 1: Use pm.response.json() to parse JSON

   This method converts the response body into a JavaScript object.

2. Step 2: Use pm.environment.set() to save variable

   Set the environment variable 'userId' with the extracted value.

3. Final Answer:

   let data = pm.response.json(); pm.environment.set('userId', data.userId); -> Option A

4. Quick Check:

   Parse JSON + set env variable = let data = pm.response.json(); pm.environment.set('userId', data.userId); [OK]

Hint: Use pm.response.json() then pm.environment.set() [OK]

Common Mistakes:

• Using pm.response.set() which doesn't exist
• Using pm.environment.get() to set variables
• Not parsing JSON before accessing properties

3. Given the response body:

{"token": "abc123", "user": {"id": 42}}

What will this Postman script save in the environment variable authToken?

let jsonData = pm.response.json();
pm.environment.set('authToken', jsonData.token);

medium

A. null

B. 42

C. undefined

D. "abc123"

Solution

1. Step 1: Parse the JSON response

   jsonData.token accesses the 'token' key which has value "abc123".

2. Step 2: Set environment variable with token value

   pm.environment.set saves "abc123" as 'authToken'.

3. Final Answer:

   "abc123" -> Option D

4. Quick Check:

   jsonData.token = "abc123" [OK]

Hint: Access exact key from parsed JSON to get value [OK]

Common Mistakes:

• Using user.id instead of token
• Expecting number 42 instead of string token
• Not parsing JSON before accessing token

4. You wrote this Postman test script to extract sessionId from the response:

let data = pm.response.json();
pm.environment.set('sessionId', data.session_id);

But the environment variable sessionId is always empty. What is the likely problem?

medium

A. pm.response.json() does not parse JSON

B. pm.environment.set() cannot save variables

C. The response JSON uses sessionId not session_id

D. You must use pm.collectionVariables.set() instead

Solution

1. Step 1: Check JSON key names carefully

   The script uses 'session_id' but the response likely has 'sessionId' (camelCase).

2. Step 2: Correct key name to match response

   Use data.sessionId to correctly extract the value.

3. Final Answer:

   The response JSON uses sessionId not session_id -> Option C

4. Quick Check:

   Key name mismatch causes empty variable [OK]

Hint: Match JSON keys exactly, including case [OK]

Common Mistakes:

• Assuming pm.environment.set() doesn't work
• Not parsing JSON before accessing keys
• Confusing environment and collection variables

5. You receive this nested JSON response:

{"data": {"users": [{"id": 1, "name": "Alice"}, {"id": 2, "name": "Bob"}]}}

How do you extract and save the name of the second user as a collection variable in Postman?

hard

A. pm.environment.set('secondUserName', pm.response.json().data.users[1].name);

B. let json = pm.response.json(); pm.collectionVariables.set('secondUserName', json.data.users[1].name);

C. let json = pm.response.json(); pm.environment.set('secondUserName', json.data.users[2].name);

D. pm.collectionVariables.set('secondUserName', pm.response.json().users[2].name);

Solution

1. Step 1: Parse the nested JSON response

   Access the array at json.data.users and select index 1 for the second user.

2. Step 2: Save the second user's name as a collection variable

   Use pm.collectionVariables.set with key 'secondUserName' and value json.data.users[1].name.

3. Final Answer:

   let json = pm.response.json(); pm.collectionVariables.set('secondUserName', json.data.users[1].name); -> Option B

4. Quick Check:

   Index 1 in users array = second user name [OK]

Hint: Use zero-based index and correct variable scope [OK]

Common Mistakes:

• Using index 2 instead of 1 for second user
• Mixing environment and collection variables
• Not parsing JSON before accessing nested data