Thanks for asking. Essentially I'd approach testing of IaC in a similar fashion.
Let's use terraform as an example here. There are some
good lower level testing approaches put together here by hashicorp.
From the view of an IDP, I would also focus on end 2 end testing of user stories. To automate this I would have tests exercising the terraform plan/apply/destroy hitting an test infrastructure environment and then verifications based on cloud APIs to check if the infra has been altered in the expected way.