[nijave]

If you're using an IaC tool like Terraform or Pulumi, you can just setup/tear down test resources on demand (for integration/acceptance tests). Under normal usage, hopefully you can get away with mocks/stubs/fakes. Some development frameworks make this a lot easier than others

Using real resources is usually fine for smaller applications but can be very problematic as your application grows. With that in mind, it's good to create boundaries so you limit the amount of "real infrastructure" you need to test/deploy. Reference https://martinfowler.com/bliki/IntegrationTest.html

[friendly_deer]

Thanks for taking the time to reply. Yeah ideally we always use real resources to mirror prod closely, but I see your point that that won’t always be possible as the app grows.

[nijave]

Another balance is to just use real resources in CI with some concurrency control to make sure a single build runs at once. Locally, you continue to use mocks/stubs/fakes

You still get assurance from testing but reduce the amount of places you run the "expensive" (time, resource, $) tests