API Requests and Chaining the Responses using Test scripts in Postman — Part 1 Authorization Tab

Postman is an API platform for building and using APIs. It gives the features of collections, test scripts which help in storing variables that can be reused.

Every HTTP requests have four main elements — An HTTP method, Request type (GET, PUT, POST, DELETE), Request HEAD/OPTIONS and Request Body.

Example of chaining responses for multiple requests

Problem statement:

How to pass dynamically generated response from one request and pass it on to other requests — i.e chaining the response from one request to another

Solution:

Step 1: Create an API collection in postman

Creating collection in Postman

Step 2: Create an environment for that collection which helps in reusing the variables within that environment.

Ex: If you have an environment added as Prod, then all the environment variables declared and values collected will be corresponding to prod requests only.

Add environment and variables here

Step 3: Create a variable in your environment (Here, env name — test_blog , variable name is registration_token)

Added environment variable

Step 4: Create your API request for which you want to collect the response variable to chain to other requests

Ex: http://restapi.adequateshop.com/api/authaccount/registration which generates Token that has to be used by Login API — /api/authaccount/login

POST Registration API with request body

Step 5: In the same POST request, write these test scripts and then Submit the request

const response = pm.response.json();

var auth_token = response.data.Token;

console.log(auth_token);

pm.environment.set(“registration_token”,auth_token)

The scripts for collecting the response and storing it to env variable for chaining it to other requests

Step 6: You can Console the results by enabling Postman Console

Console tab of Postman

Step 7: This token will be saved in environment variable.

pm.environment.set(“registration_token”,auth_token) takes care of setting the value generated in API response to the variable declared inside the environment here.

Response from the request stored as value in the variable

Step 8: Now, this token can be chained for other requests.

When Login API is hit which needs the registration token as Auth token, we can set {{registration_token}} in Authorization tab

Declare the variable in Auth tab as required

Step 9: When this API request is submitted, the token will be picked from environment variable and the response will be generated

The login API uses the response from Registration API

This explains how the login API uses the response from Registration API through response chaining in Postman

Step 10: Similarly many variables that needs to be reused can be added and chained in other requests.

This is not just applicable for Authorization tab, we can pass variables in Body tab, Params tab etc. (Continued in Part 2 of the Blog)