Hello,
I'm a Backend Software Engineer with ~3 years of working experience in a corporate environment.
I have built a lot of quality apps with Java and Spring Framework during my career.
I currently work on deploying spring boot apps as Microservices.
Since I try to achieve a high code coverage in all the projects I am working on, I am using JUnit to write my unit tests and thus I am quite familiar with it.
I think I could help you to properly mock the S3 client and have a running test.
I look forward to working with you,
Kostas