Skip to content
Postman API Testing Tips

Can We Automate Api Testing Using Postman

API Testing Blog

Automating API Testing with Postman: A Comprehensive Guide

Postman is a powerful tool that goes beyond just sending API requests. It provides a robust framework for building, testing, and documenting APIs. Let’s delve into how Postman can be leveraged for efficient API automation.

Understanding API Testing and Automation

Before jumping into the “how”, it’s crucial to understand the “why”. API testing is the process of evaluating the functionality, reliability, and security of APIs. Automation plays a pivotal role in this process, enabling:

  • Increased Efficiency: Repetitive tests can be executed automatically, freeing up time for more complex analysis.
  • Improved Accuracy: Eliminates human error inherent in manual testing.
  • Faster Feedback: Provides quick results, aiding in early bug detection.
  • Enhanced Coverage: Enables comprehensive testing scenarios, ensuring all endpoints are thoroughly examined.

The Power of Postman Collections for API Automation

Postman Collections are the key to automating API tests. They offer a structured way to organize and execute a series of API requests.

Creating a Postman Collection:

  1. Open Postman and click on “New” to create a new collection.
  2. Name your collection (e.g., “My API Tests”).
  3. Add Requests: Each request represents a specific API endpoint you want to test.

Example: GET Request in a Collection

{
  "id": "c216cf03-e5c9-421d-9c41-9ad3b4b4348e",
  "name": "Get User",
  "description": "Fetches user details by ID",
  "request": {
    "method": "GET",
    "header": [
      {
        "key": "Content-Type",
        "value": "application/json"
      }
    ],
    "url": {
      "raw": "https://api.example.com/users/1",
      "host": [
        "api",
        "example",
        "com"
      ],
      "path": [
        "users",
        "1"
      ]
    }
  },
  "response": []
}

Implementing Assertions for Verification

Postman’s built-in testing framework allows you to write assertions - checks that verify the expected behavior of your API.

Adding Assertions to a Request:

  1. Select the request you want to add assertions to.
  2. Click on “Tests” tab.
  3. Write test scripts using JavaScript:

Example: Assertions for a Status Code Check

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

Example: Assertions for JSON Response Validation

pm.test("Response body has name property", function () {
  pm.expect(pm.response.json().name).to.be.a('string');
});

Running Automated Tests with Postman

Postman offers multiple ways to execute your automated tests:

1. Manual Execution:

  • Select your collection in the Postman interface.
  • Click “Run”.
  • View results in the collection runner.

2. Scheduled Runs:

  • Go to the “Runner” tab.
  • Create a new Run.
  • Schedule the run for desired intervals (e.g., daily, weekly).
  • Receive reports via email or integrate with other tools.

3. Running Tests in the Postman API:

  • Utilize the Postman API to integrate your tests into a CI/CD pipeline.
  • Run tests directly from code using libraries like Newman.

Example – Automating a User Registration API

Scenario: Test the registration endpoint of a fictional API.

Step 1: Create a Collection

  • Name the collection “User Registration Tests”.
  • Add a request named “POST /register” with the following details:
    • Method: POST
    • URL: https://api.example.com/register
    • Headers:
      • Content-Type: application/json
    • Body:
      • Raw:
      {
        "username": "testuser",
        "email": "test@example.com",
        "password": "password123"
      }

Step 2: Add Assertions

  • In the “Tests” tab, add the following assertions:
    • Status Code Check: 
      pm.test("Status code is 201", function () {
        pm.response.to.have.status(201);
      });
    • Response Body Validation: 
      pm.test("Response body includes message", function () {
        pm.expect(pm.response.json().message).to.be.a('string');
      });

Step 3: Run the Tests

  • Manually run the collection.
  • The results will display whether the tests passed or failed.

Conclusion

Postman empowers you to seamlessly integrate API testing into your development workflow. Its intuitive interface, powerful features, and flexible options make it a go-to tool for building robust and reliable APIs. By automating API testing with Postman, you can effectively ensure the quality of your APIs and significantly enhance your overall development process.

API Testing Blog