API Testing using Postman

Testing an API end-to-end (E2E) using Postman involves several steps, from setting up the environment to creating and running test cases. Here’s a step-by-step guide to help you through the process:

Step 1: Install Postman

1. Download and Install Postman: Visit the Postman website and download the application suitable for your operating system. Install it following the on-screen instructions.
   https://www.postman.com/downloads/

Step 2: Set Up Your API Environment

1. Create an Environment:

• Open Postman and click on the Environment Quick Look icon (an eye symbol) in the top right corner.
• Click Add to create a new environment.
• Name your environment (e.g., “Development”, “Production”) and add variables like host_url, access_token, etc.

Step 3: Create API Requests

1. Create a New Collection:

• Click on the New button and select Collection.
• Name your collection (e.g., “E2E API Tests”) and add a description if needed.

1. Add Requests to the Collection:

• Inside the collection, click Add Request.
• Set the request method (GET, POST, PUT, DELETE, etc.).
• Enter the request URL. Use environment variables for dynamic URLs (e.g., {{base_url}}/api-resource).
• Add necessary headers, parameters, and body data as required by your API.

Login Request (Post Method)
Body: Username and Password in Json format where username and password are set in env variable.

Click on send button to send the Request and Server sends the response back

Step 4: Write Test Scripts

1. Add Tests to Requests:

• Go to the Tests tab of a request.
• Use JavaScript to write tests that will validate the response. Here’s an example of basic test scripts:

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

// Check if the response has a specific field
pm.test("Response has 'id' field", function () {
    var jsonData = pm.response.json();
    pm.expect(jsonData).to.have.property('id');
});

// Validate the response time
pm.test("Response time is less than 200ms", function () {
    pm.expect(pm.response.responseTime).to.be.below(200);
});

Step 5: Chain Requests

1. Set Up Pre-request Scripts:

• Go to the Pre-request Script tab of a request.
• Use JavaScript to set up variables or manipulate data before the request is sent.

// Set a variable before making the request
pm.environment.set("username", "john.doe@gmail.com");
pm.environment.set("password", "password123");

2. Use Data from Previous Requests:

• In the Tests tab, extract data from the response and store it in a variable.

var jsonData = pm.response.json();

//get the Project Name and UAN for patch Request
pm.environment.set('project_name',responseData.name)

Step 6: Run the Collection

1. Use the Collection Runner:

• Click on the Runner icon in the top left corner.
• Select your collection and environment.
• Configure the number of iterations, delay between requests, and data file (if needed).

Click Start Run to execute the requests.

2. Analyze the Results:

• After the run completes, review the results in the Collection Runner.
• Check the status of each request and ensure all tests pass.

Conclusion

By following these steps, you can set up and execute comprehensive end-to-end API tests using Postman. This process ensures your API functions correctly under various scenarios and helps catch issues early in the development cycle.