plantimestamp function not available to tests

[KyleKotowick]

Terraform Version

Terraform v1.11.3
on windows_amd64

Terraform Configuration Files

Available here as a complete config: https://github.com/Invicton-Labs/terraform-aws-plantimestamp-error

variables.tf

variable "myvar" {
  type     = string
  nullable = false
}

tests/main.tftest.hcl

# This one works fine
run "timestamp" {
  command = plan
  variables {
    myvar = timestamp()
  }
}

# This one does not
run "plantimestamp" {
  command = plan
  variables {
    # This function really should exist: 
    # https://developer.hashicorp.com/terraform/language/functions/plantimestamp
    myvar = plantimestamp()
  }
}

Debug Output

https://gist.github.com/KyleKotowick/cd54de2a28bc33326cdc6aa356163220

Expected Behavior

This function should work in tests, it certainly does exist:
https://developer.hashicorp.com/terraform/language/functions/plantimestamp

Actual Behavior

│ Error: Call to unknown function
│
│   on tests\main.tftest.hcl line 15, in run "plantimestamp":
│   15:     myvar = plantimestamp()
│
│ There is no function named "plantimestamp".

This function apparently doesn't exist for tests.

Steps to Reproduce

1. terraform test

Additional Context

No response

References

No response

Generative AI / LLM assisted development?

No response

[crw]

Thanks for this report!

[liamcervante]

Hi @KyleKotowick, thanks for filing this! This behaviour is actually working as intended. The plantimestamp() function returns a consistent timestamp computed during the plan operation. Because of this, it is not available outside of the planning context. The variables used as inputs into the Terraform operation under test are computed and assigned before the plan operation has been started so that timestamp is not available for use at that point in time.

I recognise that the docs don't make this clear though, so I have tagged this as a documentation issue and we can update the docs to highlight this function is also not available during some of the execution of a test command.