No, that's a rough guesstimate from Terrafrom on what actions it will be doing. Terratest allows you to write actual tests and mocks.

This one needs some clarification.

It’s actually not a guesstimate about what actions will be taken, it’s a guesstimate of the state that will result from those actions without any reference to ordering or “actions” as a cloud API would understand them - the plan is purely in terms of CRUD on Terraform provider resources and provisioners.

This may seem like a nit, but it fundamentally changes what Terraform is capable of doing in a single pass without external coordination.