API Requests and Chaining the Responses using Pre Request and Test scripts in Postman — Part 2 — Params, Headers & Body Tab

Refer to Part 1 of chaining API response in Authorization tab here.

Part 1 of the chaining requests Blog

Tip before going through the blog:

Pre-request script tab is useful to generate values before the execution of any API request i.e Pre API request

Tests tab is useful to collect responses from the executed API i.e Post API request

Now, let us see how to use the responses in other tabs — Params, Headers and Body

1. Params Tab Example

Step 1: Create page_number variable in environment tab

Here, if the value is going to be constant, current value can be set and reused

page_number created as env variable

Step 2: Assign the created page_number variable to the required parameter in Params tab

page_number set as a parameter that has to be passed while Getting users

Step 3: In any of your first request (here Registration of an user), test script can be written to generate static or dynamic value for this page number variable

let pageNum = Math.random();

pm.environment.set(“page_number”, pageNum);

page number can be generated statically or dynamically here

Step 4: When this API request is executed, the generated value will be stored in environment tab and can be chained/reused in other API requests

on executing the API, page number has value 2

Step 5: When the actual API request is hit, the page number will be assigned and results will be returned

Response which took page as 2

2. Headers Tab

This can be static value wherein you can set the Current value or it can be dynamic value that can be generated using Tests scripts

Example 1: Generating response using test scripts:

Step 1: Write test scripts to collect the response and store it in necessary variable

Test scripts used to generate response which can be chained

Step 2: When executed, the response will be stored in registration_token env variable

registration token generated and stored here

Step 3: Already created env variable( ex: registration_token ) or newly created ones can be imported into Headers Tab

env variable passed as value in Headers tab

Example 2: Generating static value that can be created and used.

Step 1: Here api_key is created and current value is set as test

Step 2: This variable can be passed in headers tab

variable passed as headers tab

3. Body Tab

I will also explain how Pre-request scripts can be used if random data has to be generated and reused in all the requests

Ex: For registering one user and then to login, we need to pass email id as Body parameter and we need random test data for the same.

For generating data even before execution of any request, Pre-request scripts can be used to generate value and can be stored as environment variable

Step 1: Write scripts to generate dummy data in Pre-request script and assign it to environment variable test_email_id

pre-request script

Step 2: Store the same as environment variable as test_email_id in environment tab

environment variable

Step 3: After executing the API, data will be generated and can be passed as Body parameter

Passing the value as body parameter

Conclusion: Pre-request scripts and Test scripts are useful for generating data upon execution of requests and collecting responses to chain other requests.

The series of blog on How to chain API responses to other requests will explain how to generate data and also pass the response to other requests without manual intervention every time.