Chaining request data in Postman - Test Execution Trace

Test Overview

This test sends two API requests in Postman. It verifies that data from the first response is correctly used in the second request, ensuring chaining of request data works.

Test Code - Postman

Postman

pm.test("Chaining request data test", function () {
    // First request: Get user info
    pm.sendRequest("https://jsonplaceholder.typicode.com/users/1", function (err, res) {
        pm.expect(err).to.be.null;
        pm.expect(res).to.have.property('status', 200);
        const userId = res.json().id;
        pm.expect(userId).to.eql(1);

        // Second request: Get posts by userId from first response
        pm.sendRequest({
            url: `https://jsonplaceholder.typicode.com/posts?userId=${userId}`,
            method: 'GET'
        }, function (err2, res2) {
            pm.expect(err2).to.be.null;
            pm.expect(res2).to.have.property('status', 200);
            const posts = res2.json();
            pm.expect(posts.length).to.be.greaterThan(0);
            // Check that all posts belong to userId
            posts.forEach(post => {
                pm.expect(post.userId).to.eql(userId);
            });
        });
    });
});

Execution Trace - 6 Steps

Step	Action	System State	Assertion	Result
1	Test starts	Postman test runner is ready to execute the test script	—	PASS
2	Send first GET request to https://jsonplaceholder.typicode.com/users/1	Browser/Postman sends HTTP GET request to user API endpoint	Check response status code is 200	PASS
3	Parse JSON response and extract userId	Response body contains user data with id=1	Verify userId equals 1	PASS
4	Send second GET request to https://jsonplaceholder.typicode.com/posts?userId=1 using extracted userId	Postman sends HTTP GET request to posts API with userId query parameter	Check response status code is 200	PASS
5	Parse JSON response and verify posts belong to userId=1	Response body contains array of posts with userId=1	Verify posts array length > 0 and each post.userId equals 1	PASS
6	Test ends successfully	All assertions passed, test completes	—	PASS

Failure Scenario

Failing Condition: If the first request fails or returns wrong userId, or second request returns no posts or posts with wrong userId

Execution Trace Quiz - 3 Questions

What does the first request in this test do?

A Send posts data to server

B Fetch user data and extract userId

C Delete a user

D Update user information

Key Result

Always verify that data extracted from one API response is correctly passed and used in subsequent requests to ensure reliable chaining.

Practice

1. What is the main purpose of chaining request data in Postman?

easy

A. To pass data from one API request to another for connected testing

B. To run multiple requests at the same time

C. To change the request method automatically

D. To generate random data for each request

Solution

1. Step 1: Understand chaining request data

   Chaining request data means using data from one API response in the next request to keep tests connected.

2. Step 2: Identify the purpose

   This helps simulate real user flows where one action depends on the previous one.

3. Final Answer:

   To pass data from one API request to another for connected testing -> Option A

4. Quick Check:

   Chaining = passing data between requests [OK]

Hint: Chaining means passing data forward between requests [OK]

Common Mistakes:

• Thinking chaining runs requests simultaneously
• Confusing chaining with changing HTTP methods
• Assuming chaining generates random data

2. Which Postman script correctly saves a value from a JSON response to an environment variable named userId?

easy

A. pm.response.set('userId', pm.environment.json().id);

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

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

D. pm.environment.set('userId', pm.response.json().id);

Solution

1. Step 1: Identify correct method to save variable

   Use pm.environment.set(key, value) to save data to environment variables.

2. Step 2: Extract value from response JSON

   Use pm.response.json() to parse JSON and get the id field.

3. Final Answer:

   pm.environment.set('userId', pm.response.json().id); -> Option D

4. Quick Check:

   Set environment variable = pm.environment.set [OK]

Hint: Use pm.environment.set to save data from pm.response.json() [OK]

Common Mistakes:

• Using pm.environment.get to set a variable
• Confusing pm.response and pm.environment methods
• Trying to get data from environment instead of response

3. Given this Postman test script after a request:

const jsonData = pm.response.json();
pm.environment.set('token', jsonData.auth.token);

What will be the value of the environment variable token if the response JSON is {"auth": {"token": "abc123"}}?

medium

A. null

B. undefined

C. "abc123"

D. Error: token not found

Solution

1. Step 1: Parse the response JSON

   The response JSON has an object with auth containing token with value "abc123".

2. Step 2: Set environment variable

   The script sets token variable to jsonData.auth.token, which is "abc123".

3. Final Answer:

   "abc123" -> Option C

4. Quick Check:

   token value = "abc123" [OK]

Hint: Check JSON path matches response structure exactly [OK]

Common Mistakes:

• Assuming token is undefined if nested
• Forgetting to parse JSON before accessing
• Expecting error when token exists

4. You wrote this script to chain data:

const data = pm.response.json();
pm.environment.set('userId', data.user.id);

But the environment variable userId is always empty after the request. What is the likely problem?

medium

A. The script must run before the request

B. The response JSON does not have a user object

C. You must use pm.variables.set instead

D. pm.environment.set cannot save variables

Solution

1. Step 1: Check JSON structure

   If data.user is undefined, accessing data.user.id returns undefined, so variable is empty.

2. Step 2: Confirm environment.set works correctly

   pm.environment.set works if given a valid value, so problem is likely missing user in response.

3. Final Answer:

   The response JSON does not have a user object -> Option B

4. Quick Check:

   Missing JSON key = empty variable [OK]

Hint: Verify JSON keys exist before accessing nested values [OK]

Common Mistakes:

• Assuming pm.environment.set is broken
• Using wrong method like pm.variables.set
• Running script before response is received

5. You want to chain two requests where the first returns a list of users:

{"users": [{"id": 1}, {"id": 2}]}

You want to save the id of the first user to an environment variable firstUserId and use it in the second request URL as /users/{{firstUserId}}. Which script correctly does this in the first request's Tests tab?

hard

A. const jsonData = pm.response.json();
pm.environment.set('firstUserId', jsonData.users[0].id);

B. const jsonData = pm.response.json();
pm.environment.set('firstUserId', jsonData.users.id[0]);

C. const jsonData = pm.response.json();
pm.environment.set('firstUserId', jsonData.users[1].id);

D. const jsonData = pm.response.json();
pm.environment.set('firstUserId', jsonData.user[0].id);

Solution

1. Step 1: Parse response JSON correctly

   The response has a users array with objects containing id. The first user is at index 0.

2. Step 2: Save first user's id properly

   Access jsonData.users[0].id and save it with pm.environment.set.

3. Final Answer:

   const jsonData = pm.response.json(); pm.environment.set('firstUserId', jsonData.users[0].id); -> Option A

4. Quick Check:

   Array index 0 for first user id [OK]

Hint: Use array index [0] to get first item in JSON array [OK]

Common Mistakes:

• Using wrong array index or property name
• Accessing id as users.id[0] instead of users[0].id
• Using singular 'user' instead of 'users'