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Postman API Testing Tips

What Language Postman Uses

API Testing Blog

Understanding the Languages Behind Postman

Postman is a popular API platform used for testing, documenting, and sharing APIs. While it offers a user-friendly interface, it’s built upon several programming languages and frameworks that make it powerful and versatile.

Postman’s Core Language: JavaScript

At its heart, Postman utilizes JavaScript as its primary scripting language. This means you can write code directly within Postman to automate tasks, manipulate data, and create dynamic API interactions.

  • Example: Send a POST request to a JSONPlaceholder API endpoint, adding a random integer to the ‘id’ field:
const randomId = Math.floor(Math.random() * 100) + 1;


pm.test("Random ID added to request", () => {
  pm.expect(pm.request.body.raw).to.include(randomId.toString());
});


pm.request.body.raw = JSON.stringify({
  "userId": 1,
  "id": randomId,
  "title": "new task",
  "completed": false
});

Postman’s Ecosystem: Supporting Languages

Postman’s ecosystem isn’t limited to JavaScript. It integrates with other languages and tools via its robust collection of features:

1. Environment Variables for Dynamic Values:

  • Environments allow you to manage different API endpoints (e.g., development, staging, production) and other values by using variables.
  • You can access these variables within your scripts using a syntax like this: pm.environment.get("your_variable_name").

2. Pre-Request Scripts and Tests:

  • These scripts provide a structured way to execute code before sending a request or validating a response.
  • You can use JavaScript in combination with libraries like chai for assertions, making your tests more comprehensive.

3. Collections and Workspaces:

  • Collections organize your API requests into folders and share them easily with teams.
  • Workspaces allow collaboration, version control, and team-wide visibility of API projects.

4. Integration with Other Tools:

  • Postman plugs seamlessly into other tools such as CI/CD systems, databases, Git repositories, and more.
  • This integration allows automating workflows, managing API change requests, and integrating with your existing development pipelines.

Example with Environment Variable and Pre-Request Script

1. Setting up an Environment Variable:

  • Create a new environment in Postman and add a variable called api_base_url.

2. Writing a Pre-Request Script:

pm.environment.set("endpoint", pm.environment.get("api_base_url") + "/posts");

3. Sending a GET request to the endpoint:

  • Use the pm.environment.get("endpoint") in the request URL.

4. Adding a Test Script:

pm.test("Status code is 200", function () {
  pm.response.to.have.status(200);
});

This example demonstrates how to use environmental variables and pre-request scripts to make your code reusable and manage various API configurations effectively.

Summary: Postman’s Language Power

In essence, Postman is built on JavaScript, but it empowers you to work with other languages and tools through its ecosystem. This combination makes it a versatile platform for managing, testing, and sharing APIs for both individual developers and entire development teams.

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