Mocked module executing code in test scenario

OpenTofu v1.12.6
on darwin_arm64
+ provider registry.opentofu.org/hashicorp/aws v6.62.0
+ provider registry.opentofu.org/hashicorp/external v2.4.1
+ provider registry.opentofu.org/hashicorp/local v2.9.0
+ provider registry.opentofu.org/hashicorp/null v3.3.1

module "lambda_function" {
  source  = "terraform-aws-modules/lambda/aws"
  version = "8.8.0"

  function_name = "my-lambda1"
  description   = "My awesome lambda function"
  handler       = "index.lambda_handler"
  runtime       = "python3.12"

  source_path = "./src/lambda-function1"

  tags = {
    Name = "my-lambda1"
  }
}

mock_provider "aws" {
}

run "bare_minimum_test" {
  command = plan

  override_module {
    target = module.lambda_function
    outputs = {
      lambda_function_arn = "arn:aws:lambda:eu-west-1:123456789012:function:lambda-eu-west-1-test123"
    }
  }

  assert {
    condition     = output.lambda_function_arn != ""
    error_message = "The Lambda function ARN should not be empty."
  }
}

tests/basic.tftest.hcl... fail
  run "bare_minimum_test"... fail
╷
│ Error: Invalid index
│ 
│   on .terraform/modules/lambda/main.tf line 15, in locals:
│   15:   source_code_hash = var.ignore_source_code_hash ? null : (terraform_data.package_filename_for_hash[0].output.filename != null ? try(filebase64sha256(terraform_data.package_filename_for_hash[0].output.filename), null) : null)
│     ├────────────────
│     │ terraform_data.package_filename_for_hash is empty tuple
│ 
│ The given key does not identify an element in this collection value: the collection has no elements.
╵

Failure! 0 passed, 1 failed.