Skip to content
Postman API Testing Tips

How To Use Postman To Teat Apis

API Testing Blog

Understanding Postman: The API Testing Tool

Postman is a popular and powerful platform for building, testing, documenting, and sharing APIs. It provides a user-friendly interface and a wide range of features that make it an indispensable tool for API testing. In this guide, we’ll explore how to leverage Postman’s capabilities to effectively test APIs.

1. Setting up Postman

  • Download and Install: Start by downloading and installing Postman from https://www.postman.com/. Choose the appropriate version for your operating system.
  • Create an Account: Sign up for a free Postman account to access various features like team collaboration and cloud-based storage.
  • Launch Postman: After installation, fire up Postman and you’ll be greeted with a clean and intuitive interface.

2. Creating Your First Request

Let’s begin with a simple GET request to fetch data from a public API:

  • Open a New Request: Click the “New” button in the top left corner and select “Request” to start crafting your API call.
  • Enter Request Details:
    • Method: Select “GET” from the drop-down menu for this example.
    • URL: Paste the API endpoint you want to test. For instance, use https://api.github.com/users/octocat to retrieve information about the “octocat” user on GitHub.
  • Send the Request: Hit the “Send” button. Postman will execute the request and display the server’s response in the right pane.

3. Inspecting the Response

Postman provides a comprehensive view of the API response:

  • Status Code: This indicates the success or failure of the request. A 200 status code signifies a successful request, while 400 series codes indicate errors.
  • Headers: Here you’ll find meta-information about the response, such as the content type, server details, and more.
  • Body: The content of the response. This might be JSON, XML, text, or other formats depending on the API.

4. Using Variables for Dynamic Testing

Variables make your tests reusable and adaptable:

  • Define Variables: Click on the “Variables” tab in the left sidebar of Postman and define variables for your URL, headers, or other parameters. You can use the “Set a Variable” feature to dynamically change the values in your requests.
  • Example: Create a variable named username and assign “octocat” to it. Modify the URL to use this variable: https://api.github.com/users/{{username}}. Now, changing the variable value in Postman will automatically update the request target.

5. Authentication in Postman

Many APIs require authentication for access:

  • Basic Auth: For basic authentication, enter your username and password in the “Authorization” tab and choose “Basic Auth”.
  • OAuth 2.0: Choose “OAuth 2.0” for APIs using this common authorization method. You’ll need to configure various settings, such as the client ID and secret, to successfully authenticate.
  • Other Methods: Postman supports various other authentication mechanisms like API keys, Bearer tokens, and more.

6. Sending Different Request Types

Postman allows you to send diverse HTTP requests:

  • POST: Sends data to the server for creation or modification.
  • PUT: Replaces existing data with complete new data.
  • PATCH: Updates or modifies specific parts of the data.
  • DELETE: Deletes data from the server.

For each request type, you can configure the necessary parameters, headers, and body data.

7. Assertions and Testing

To rigorously test your API, use assertions to verify expected behaviors:

  • Test Tab: Open the “Test” tab within a request.
  • Writing Assertions: Use JavaScript code to define your assertions. For instance: 
    pm.test("Status code is 200", function () {
        pm.response.to.have.status(200);
    });
    

    pm.test("Response body contains 'octocat'", function () {
        pm.expect(pm.response.text()).to.include('octocat');
    });
  • Run Tests: Send the request, and Postman will execute your assertions and display the results.

8. Building Collections and Organizing Your Tests

  • Creating Collections: Collections allow you to group related requests and tests together. This makes your API workflow organized and efficient.
  • Sharing Collections: You can share your collections with teammates or publicly to facilitate collaboration and knowledge sharing.

Conclusion

Postman is a powerful and versatile tool that empowers you to efficiently test your APIs. This guide has introduced the core features of Postman, covering request creation, response analysis, variables, authentication, advanced request types, assertions, and collection management. As you continue to explore Postman, you can delve into more advanced features like environment variables, mock servers, and more to build comprehensive API testing workflows.

API Testing Blog