How to handle unit test / integration test for a Installation / Setup Application that can be used in multiple platform such as Windows, Linux, Unix

I'm handling a code repository that is responsible to deploy / install / upgrade agent that are running on different platform, windows, unix, linux.

The code base already has some unit test to cover the behavior of important component.

I'm now thinking how I could increase the test coverage and confidence of the setup / upgrade by introducing integration testing, and integrate with travis.

What are the available test framework that I could explore on this type of application?