What Is Postman Scripting?


Angela Bailey

Postman Scripting: Taking API Testing to the Next Level

Postman is a powerful tool for testing and working with APIs. It provides a user-friendly interface to send requests, inspect responses, and automate API testing.

But did you know that Postman also supports scripting? With Postman scripting, you can take your API testing to the next level by adding custom logic and automation.

What is Postman Scripting?

Postman scripting allows you to write custom JavaScript code that runs before or after a request is sent. This gives you the ability to manipulate request parameters, extract data from responses, and perform complex test scenarios.

Why use Postman Scripting?

Postman already provides a wide range of features for testing APIs, such as assertions and variables. However, there are cases where you may need more flexibility and control over your tests. Here are some scenarios where Postman scripting can be beneficial:

  • Data Manipulation: You can modify request parameters or response data using JavaScript code. For example, if you need to generate dynamic values in your requests or extract specific data from the response for further processing.
  • Complex Scenarios: With scripting, you can create intricate test scenarios involving multiple requests and conditional logic.

    This allows you to simulate real-world use cases more accurately.

  • Data-Driven Testing: By reading data from external sources like CSV files or databases, you can create data-driven tests that iterate over multiple sets of input values.
  • Integration with External Systems: You can interact with external systems or services in your scripts. This opens up possibilities for integrating with other tools or performing additional actions.

How does Postman Scripting work?

Postman scripting uses JavaScript, a popular and powerful scripting language. The scripts can be written within the Postman application itself, eliminating the need for external tools or dependencies.

Postman provides two types of scripts: Pre-request Scripts and Tests Scripts.

Pre-request Scripts

A pre-request script is executed before sending a request. It allows you to modify request parameters and headers dynamically. This is useful when you need to generate random values, add authentication tokens, or set conditional headers based on certain criteria.

Tests Scripts

A test script runs after receiving a response. It enables you to perform various operations on the response data like extracting values, validating responses against expected results, and setting global variables for subsequent requests.

Writing Postman Scripts

To write a script in Postman, navigate to the “Pre-request Script” or “Test Script” section of your request. You will find an editor where you can enter your JavaScript code.

In your script, you can access different variables and functions provided by Postman. For example, you can use the pm.request object to access request details or the pm.response object to access response data. Additionally, Postman provides helper functions like pm.environment.get(), which allows you to retrieve values from environment variables.

You can also utilize JavaScript libraries in your scripts by adding them as dependencies in the Postman application. This gives you access to additional functionalities and makes it easier to work with complex scenarios.

Tips for Effective Postman Scripting

  • Simplify and Reuse: Break down your scripts into smaller functions that can be reused across multiple requests. This improves maintainability and reduces duplication.
  • Debugging: Use console.log statements to print debugging information in the Postman console.

    This helps you troubleshoot issues and understand the flow of your scripts.

  • Documentation: Comment your code to explain the logic and purpose of each script. Proper documentation makes it easier for others to understand and collaborate on your tests.


Postman scripting is a powerful feature that enhances your API testing capabilities. It allows you to add custom logic, automate repetitive tasks, and handle complex scenarios. Whether you need to manipulate data, create data-driven tests, or integrate with external systems, Postman scripting has got you covered.

By leveraging JavaScript and the various features provided by Postman, you can create robust and efficient API tests that deliver accurate results. So why not give Postman scripting a try and take your API testing to the next level?

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