Ask HN: How do you test your docker images/docker-compose deployments?

When I'm writing docker services or docker images, I have to test it all manually and hope for the best.

But it's tedious and error-prone. Ideally, I'd want to check that a specific file is there with specific contents, or that when launching a container I can access a specific URL, etc.

What do you use for CI testing of Docker images and Docker services? Is there a best practice for doing that?