Support for mocking providers in opentofu test

[tv-sister]

OpenTofu Version

OpenTofu v1.6.0

Use Cases

Test OpenTofu code offline.

Attempted Solutions

Using fake credentials in your provider in the testfile does not always work, the newly implemented mock provider by Terraform has a broader usecase, as it allows faking data sources etc.

https://developer.hashicorp.com/terraform/language/tests/mocking

For example, using fake credentials and trying to retrieve an AMI with

data "aws_ami" "ubuntu" {
  most_recent = true

  filter {
    name   = "name"
    values = ["ubuntu/images/hvm-ssd/ubuntu-jammy-22.04-amd64-server-*"]
  }

  filter {
    name   = "virtualization-type"
    values = ["hvm"]
  }

  owners = ["099720109477"] # Canonical
}

Returns the following error

reading EC2 AMIs: AuthFailure: AWS was not able to validate the provided access credentials

Proposal

Add support for mocking providers, resources, and data sources.

References

No response

[cube2222]

Thanks for submitting the issue @tv-sister!

We've agreed that this makes sense for compatibility purposes, and the core team will pick it up with the goal being a release of this alongside 1.7.0.

[RLRabinowitz]

When taking this task, and if deciding to use the same syntax as Terraform does (.tfmock.hcl files), make sure these files would be included in the tofu fmt command run - hashicorp/terraform#34577

[RLRabinowitz]

Also - keep this possible crash in mind - hashicorp/terraform#34601