Ask HN: How to get OSx test environment?

I'm trying to build a python library as a side project. I test the ubuntu installations and other features by either running VMs or vagrant.

How do I get fresh OSx environment for testing? (Multiple versions of OSx). Is there something that I can use in a manner similar to vagrant ?

How does one do testing on OSx without having to buy different machines.

Thanks for all the help and guidance.