In this section, we will explore how to chain requests in Postman, a powerful technique that allows you to execute multiple API requests in a sequence, using the output of one request as the input for the next. This is particularly useful for testing workflows that require multiple steps, such as user authentication followed by data retrieval.

1. Request Chaining: The process of using the response from one API request as the input for another request.
2. Environment and Global Variables: Variables that can be used to store data from responses and pass it to subsequent requests.
3. Pre-request and Test Scripts: JavaScript code that can be executed before a request is sent or after a response is received, allowing for dynamic data handling.

Let's walk through a practical example of chaining requests using Postman.

You have an API that requires user authentication before accessing user data. The workflow involves:

1. Sending a login request to obtain an authentication token.
2. Using the token to fetch user details.

Step 1: Create a Login Request

1. Create a new request in Postman.
2. Set the request type to POST and enter the login endpoint URL (e.g., https://api.example.com/login).
3. In the Body tab, select raw and JSON format, then enter the login credentials:

   {
     "username": "[email protected]",
     "password": "securepassword"
   }
   

4. Click Send to execute the request.

Step 2: Extract the Authentication Token

1. In the Tests tab of the login request, add the following script to extract the token from the response and save it as an environment variable:

   pm.test("Extract token", function () {
     var jsonData = pm.response.json();
     pm.environment.set("authToken", jsonData.token);
   });
   

   • This script parses the JSON response and sets the authToken variable with the token value.

Step 3: Create a User Details Request

1. Create another request in Postman.
2. Set the request type to GET and enter the user details endpoint URL (e.g., https://api.example.com/user).
3. In the Headers tab, add an Authorization header with the value Bearer {{authToken}}.
   • The {{authToken}} is a placeholder that will be replaced with the actual token value from the environment variable.
4. Click Send to execute the request.

Task: Create a sequence of requests to register a new user and then retrieve their profile information.

1. Register User: Create a POST request to /register with user details.
2. Extract User ID: Use a test script to save the user ID from the response.
3. Get User Profile: Create a GET request to /profile/{{userId}} using the extracted user ID.

1. Register User Request:

   {
     "username": "[email protected]",
     "password": "newpassword"
   }
   

   • Test Script:

     pm.test("Extract user ID", function () {
       var jsonData = pm.response.json();
       pm.environment.set("userId", jsonData.id);
     });
     

2. Get User Profile Request:

   • URL: /profile/{{userId}}

• Mistake: Forgetting to set the environment variable after extracting data.
  • Tip: Always verify that the variable is set correctly by checking the environment variables in Postman.
• Mistake: Using incorrect variable syntax in headers or URLs.
  • Tip: Ensure variables are enclosed in double curly braces {{}}.

Chaining requests in Postman is a powerful technique for testing complex API workflows. By using environment variables and scripts, you can dynamically pass data between requests, making your tests more robust and flexible. In the next section, we will delve into using Postman scripts to further enhance your testing capabilities.