Create unit test for File handling API endpoints

[azharem]

As a developer I want to create unit test for File uploading API endpoints so that we can test the endpoints for bugs.

I know this is done when:

• [ ] Unit test exists for success scenario for file upload
• [ ] Unit test exists for failure scenario for file upload
• [ ] Unit test exists for success scenario for downloading existing file
• [ ] Unit test exists for failure scenario for downloading existing file
• [ ] Unit test exists for success scenario for removing a file from existing files
• [ ] Unit test exists for failure scenario for removing a file from existing files
• [ ] All of the above tests run successfully