How to test code written against AWS API

Question

Please help me out in this:

As I'm writing an application in Java that uploads a file to AWS S3.
The file is given to the application into an argument, not hardcoded.

I wish to write tests, so as to ensure that the file is actually getting uploaded to my S3. The test gets written before the code for TDD. I myself have written the code already, but I want to ingrain TDD practices into all of my work to gain a habit.

I will be using JUnit as that's what I'm most familiar with. So, how precisely I can do this?

Answer 1

The actual uploading and the tests that u are doing are a part of your integration testing, not the unit testing.

If you wrap the S3 API in a very thin class, you will mock that class for unit testing of your business classes, and you will use the real implementation for integration testing.

If you have decided, your business classes to take directly the AmazonS3 interface, then for unit testing you have to mock that one.

The actual exploratory testing (learning and verifying) if and how amazon s3 works is what you actually do in separate experimental setup.

BTW I do not recommend using the AmazonS3 interface directly in your business classes, rather, wrap it in a thin interface of yours, so that if you decide to change the 'back-end storage' you can easily change it.