You can now easily test your Drupal projects on AppVeyor. Currently, AppVeyor is the major player in CI regarding Windows Servers. On other CI systems (Travis, Bitbucket pipelines) you are limited to Docker containers for the *nix platform. (This will soon change as some CI will throw Windows containers into the mix).
Until then, the only tool to CI your Drupal (or any PHP project) on a Windows based environment using IIS is AppVeyor.