How to test crossplatform C++ code?

[egslava]

Hello, everyone!
I've implemented a simple library in C++ and uploaded it on github. Now I want to be sure, that it works on Windows/Linux/OS X. I have some background in Java/Python and only a bit of C++. So, in Java, I'd just go with simple unit-tests and I'd be sure that it works, then, it should work everywhere. The same with Python.

But now I did the lib in C++ and I want to ensure, that it is at least buildable under Windows/Linux and OS X. I want to be sure, that my small library runs everywhere.

My wife has MacBookPro and I own a laptop with Ubuntu 16.04 and a PC with Windows 8.

I see few options:
A. 
Just do it:
1. Check on Windows machine.
2. Copy&paste to Ubuntu machine, start Qt Studio and run it there.
3. The same for OS X. It's the most uncomfortable part, since I'm not the owner of the macbook.

B. 
1. Install SSH daemons on all the machines.
2. Install git and cmake on all the machines as well.
3. run git pull and ctest remotely.
So, overall it should look like: ssh user@ubuntu_laptop 'bash -s' < git_pull_ctest.sh

What I wonder about: how is it usually implemented in C++ projects? What's a 'golden standard' for such kinds of things? What would you do?

Thank you for you attention!