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How To Test File Download Rest Api Using Postman

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Testing File Download REST APIs with Postman

Postman, with its versatile features, is an excellent tool for testing file download REST APIs. In this guide, we’ll walk through the process, covering everything from setting up the request to verifying the downloaded file.

1. Setting Up the Request

Before making the request, ensure you have the following information:

  • API Endpoint: The URL to access the file download API.
  • Authorization: Any required authentication methods (API key, token, etc.).
  • Request Method: This is usually GET, but could be POST if the API requires additional parameters.

Here’s an example using a GET request with a simple API key authorization:

// Example API Endpoint
https://api.example.com/download/file/{file_id}


// Example API Key
YOUR_API_KEY


// Setting up the Postman request:
- Go to the Postman interface and select the "GET" request method.
- Paste the API endpoint into the "URL" field, replacing "{file_id}" with the actual file ID.
- Under the "Headers" tab, add a new key-value pair:
    - Key: Authorization
    - Value: Bearer YOUR_API_KEY

2. Sending the Request and Handling the Response

The next step is sending the request and examining the response.

  • Sending the Request: Click the “Send” button in Postman.
  • Response Code: The API should return a success code (typically 200 OK) if the download is initiated correctly.
  • Content-Disposition Header: Check the Content-Disposition header in the response. It will indicate the file name and suggest how the browser should handle the downloaded file.

3. Downloading and Verifying the File

Postman allows you to download the file directly.

  • Downloading the File: Navigate to the “Body” tab in the response. You should see the raw content of the downloaded file. Postman offers the option to “Download file” directly.
  • Verification: After downloading the file, perform checks to ensure:
    • File Size: Compare the actual file size to the expected size.
    • File Type: Confirm that the file type matches the expected format.
    • Content Integrity: Depending on the file type, open the file and verify its content is as expected. You might want to use checksums or other validation methods for critical files.

4. Using Postman’s Tests to Automate Verification

Postman’s “Tests” tab allows you to create automated tests to verify the download process.

  • Creating a Test Script: Write a test script in the “Tests” tab to perform the desired checks. Here’s an example script to verify the response code, header, and file size:
pm.test("Status code is 200", function () {
    pm.response.to.have.status(200);
});


pm.test("Content-Disposition header is set", function () {
    pm.expect(pm.response.headers.get('Content-Disposition')).to.be.not.null;
});


pm.test("File size is correct", function () {
    pm.expect(pm.response.headers.get('Content-Length')).to.equal(1024);  // Replace with the expected size
});

5. Testing File Download with Different File Types

Test the API with various file types to ensure it handles different formats correctly. Follow similar steps as outlined above but keep in mind:

  • Content-Type Header: The Content-Type header will identify the file type.
  • File Verification: The verification process should be tailored for each specific file type.

6. Testing Different Error Scenarios

Test how the API handles potential errors:

  • Invalid File ID: Use an invalid file ID in the URL to see if the API returns an appropriate error message.
  • Unauthorized Access: Test the API without providing valid authentication credentials.
  • File Not Found: Try downloading a file that does not exist on the server.

By using Postman for testing file download REST APIs, you can quickly and effectively verify the functionality, content, and performance of your API while ensuring a smooth download experience for your users.

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