Flow creation in Postman

Introduction

Flow creation helps you automate a series of API requests and checks in Postman. It saves time and ensures your APIs work as expected step-by-step.

You want to test a login API, then use the token in the next request automatically.

You need to check if creating a user works before updating that user.

You want to run multiple API calls in order and verify each response.

You want to automate repetitive API tests without manual clicks.

Syntax

Postman

1. Create a new collection in Postman.
2. Add requests in the order you want them to run.
3. Use 'Tests' tab in each request to write JavaScript code for checks.
4. Use 'Pre-request Script' tab to set variables or prepare data.
5. Run the collection using the Collection Runner or Monitor.

Each request can pass data to the next using environment or collection variables.

Tests use JavaScript and Postman API like pm.test() and pm.response.

Examples

This example checks the response status and saves a token to use later.

Postman

// In Tests tab of first request
pm.test('Status is 200', () => {
  pm.response.to.have.status(200);
});

// Save token for next request
const jsonData = pm.response.json();
pm.environment.set('token', jsonData.token);

This adds the saved token as an Authorization header before the second request runs.

Postman

// In Pre-request Script of second request
pm.request.headers.add({key: 'Authorization', value: `Bearer ${pm.environment.get('token')}`});

Sample Program

This flow logs in first, saves the token, then uses it to get the user profile and checks the response.

Postman

// Collection with two requests
// Request 1: Login API
// Tests tab:
pm.test('Login success', () => {
  pm.response.to.have.status(200);
  const data = pm.response.json();
  pm.environment.set('authToken', data.token);
});

// Request 2: Get user profile
// Pre-request Script:
pm.request.headers.add({key: 'Authorization', value: `Bearer ${pm.environment.get('authToken')}`});

// Tests tab:
pm.test('Profile fetched', () => {
  pm.response.to.have.status(200);
  pm.expect(pm.response.json()).to.have.property('username');
});

Important Notes

Always clear or reset environment variables before running flows to avoid stale data.

Use descriptive test names to understand results easily in reports.

Flows help catch errors early by testing APIs in real usage order.

Summary

Flow creation automates API tests in Postman by chaining requests.

Use Tests and Pre-request Scripts to pass data and check responses.

Run flows with Collection Runner to see step-by-step results.

Practice

1. What is the main purpose of creating a flow in Postman?

easy

A. To automate API tests by chaining multiple requests

B. To write SQL queries inside Postman

C. To design user interfaces for APIs

D. To create database backups automatically

Solution

1. Step 1: Understand flow creation in Postman

   Flow creation means linking API requests so they run one after another automatically.

2. Step 2: Identify the purpose of chaining requests

   Chaining helps automate tests by passing data between requests and checking responses.

3. Final Answer:

   To automate API tests by chaining multiple requests -> Option A

4. Quick Check:

   Flow creation = automate chained API tests [OK]

Hint: Flows chain requests to automate tests quickly [OK]

Common Mistakes:

• Confusing flow creation with UI design
• Thinking flow creates database backups
• Assuming flow writes SQL queries

2. Which Postman script section is used to pass data from one request to the next in a flow?

easy

A. Pre-request Script

B. Headers

C. Tests

D. Body

Solution

1. Step 1: Identify where to save data after a request

   The Tests script runs after a request and can save response data to variables.

2. Step 2: Understand data passing in flows

   Saved variables from Tests can be used in the next request's Pre-request Script or URL.

3. Final Answer:

   Tests -> Option C

4. Quick Check:

   Data passing happens in Tests script [OK]

Hint: Use Tests to save data for next request [OK]

Common Mistakes:

• Using Body to pass data between requests
• Confusing Pre-request Script as data saver
• Trying to pass data via Headers

3. Consider this Postman Tests script snippet:
pm.environment.set('token', pm.response.json().access_token);
What will be the value of token after this runs if the response JSON is {"access_token": "abc123"}?

medium

A. undefined

B. "abc123"

C. pm.response.json()

D. null

Solution

1. Step 1: Extract value from response JSON

   The code accesses the 'access_token' key from the JSON response, which is "abc123".

2. Step 2: Store value in environment variable

   pm.environment.set saves "abc123" as the value of 'token'.

3. Final Answer:

   "abc123" -> Option B

4. Quick Check:

   token = "abc123" after set [OK]

Hint: pm.environment.set stores exact JSON key value [OK]

Common Mistakes:

• Assuming token becomes undefined
• Confusing the whole JSON with the value
• Expecting null instead of actual token

4. You wrote this Pre-request Script to use a token saved in environment variables:
pm.request.headers.add({key: 'Authorization', value: 'Bearer ' + pm.environment.get('token')});
But the API returns 401 Unauthorized. What is the likely error?

medium

A. Bearer keyword should be lowercase 'bearer'

B. The header key should be lowercase 'authorization'

C. pm.request.headers.add is not valid syntax

D. The token variable is not set or is empty

Solution

1. Step 1: Check if token variable exists

   If 'token' is missing or empty, the Authorization header will be invalid.

2. Step 2: Verify header syntax and casing

   Header keys are case-insensitive, and 'Bearer' is case-sensitive but usually uppercase works fine.

3. Step 3: Confirm method usage

   pm.request.headers.add is valid to add headers dynamically.

4. Final Answer:

   The token variable is not set or is empty -> Option D

5. Quick Check:

   Missing token causes 401 Unauthorized [OK]

Hint: Check if token variable is set before request [OK]

Common Mistakes:

• Changing header key case unnecessarily
• Lowercasing 'Bearer' keyword
• Thinking pm.request.headers.add is invalid

5. You want to create a flow where the first request logs in and saves a token, and the second request uses that token in its header. Which steps correctly describe this flow setup?

hard

A. In first request Tests, save token to environment; in second request Pre-request Script, add Authorization header using saved token

B. In first request Body, save token; in second request Tests, add Authorization header

C. In first request Headers, save token; in second request Body, add Authorization header

D. In first request Pre-request Script, save token; in second request Tests, add Authorization header

Solution

1. Step 1: Save token after login request

   Use Tests script in first request to extract token from response and save it to environment variables.

2. Step 2: Use token before second request

   In second request's Pre-request Script, read the saved token and add it to the Authorization header.

3. Final Answer:

   In first request Tests, save token to environment; in second request Pre-request Script, add Authorization header using saved token -> Option A

4. Quick Check:

   Save token in Tests, use in Pre-request Script [OK]

Hint: Save token in Tests, use in Pre-request Script for next request [OK]

Common Mistakes:

• Trying to save token in Body or Headers
• Adding header in Tests instead of Pre-request Script
• Saving token before request runs