Mocking Terraform Sentinel Data
We recommend that you test your Sentinel policies extensively before deploying them within HCP Terraform. An important part of this process is mocking the data that you wish your policies to operate on.
Note: HCP Terraform Free Edition includes one policy set of up to five policies. In HCP Terraform Plus Edition, you can connect a policy set to a version control repository or create policy set versions via the API. Refer to HCP Terraform pricing for details.
Due to the highly variable structure of data that can be produced by an individual Terraform configuration, HCP Terraform provides the ability to generate mock data from existing configurations. This can be used to create sample data for a new policy, or data to reproduce issues in an existing one.
Testing policies is done using the Sentinel CLI. More general information on testing Sentinel policies can be found in the Testing section of the Sentinel runtime documentation.
Be careful! Mock data generated by HCP Terraform directly exposes any and all data within the configuration, plan, and state. Terraform attempts to scrub sensitive data from these mocks, but we do not guarantee 100% accuracy. Treat this data with care, and avoid generating mocks with live sensitive data when possible. Access to this information requires permission to download Sentinel mocks for the workspace where the data was generated.
Generating Mock Data Using the UI
Mock data can be generated using the UI by expanding the plan status section of the run page, and clicking on the Download Sentinel mocks button.
For more information on creating a run, see the Terraform Runs and Remote Operations section of the docs.
If the button is not visible, then the plan is ineligible for mock generation or the user doesn't have the necessary permissions. See Mock Data Availability for more details.
Generating Mock Data Using the API
Mock data can also be created with the Plan Export API.
Multiple steps are required for mock generation. The export process is asynchronous, so you must monitor the request to know when the data is generated and available for download.
- Get the plan ID for the run that you want to generate the mock for by
getting the run details.
Look for the
id
of theplan
object within therelationships
section of the return data. - Request a plan
export using the
discovered plan ID. Supply the Sentinel export type
sentinel-mock-bundle-v0
. - Monitor the export request by viewing the plan
export. When the
status is
finished
, the data is ready for download. - Finally, download the export data. You have up to an hour from the completion of the export request - after that, the mock data expires and must be re-generated.
Using Mock Data
Note: The v2 mock files are only available on Terraform 0.12 and higher.
Mock data is supplied as a bundled tarball, containing the following files:
The sample sentinel.hcl
file contains mappings to the mocks so that you
can get started testing with sentinel apply
right away. For sentinel test
,
however, we recommend a more detailed layout.
We recommend placing the files for sentinel test
in a subdirectory
of the repository holding your policies, so they don't interfere with the
command's automatic policy detection. While the test data is Sentinel code, it's
not a policy and will produce errors if evaluated like one.
Each configuration that needs access to the mock should reference the mock data
files within the mock
block in the Sentinel configuration file.
For sentinel apply
, this path is relative to the working directory. Assuming
you always run this command from the repository root, the sentinel.hcl
configuration file would look like:
For sentinel test
, the paths are relative to the specific test configuration
file. For example, the contents of pass.json
, asserting that the result of the
main
rule was true
, would be:
Mock Data Availability
The following factors can prevent you from generating mock data:
- You do not have permission to download Sentinel mocks for the workspace. (More about permissions.) Permission is required to protect the possibly sensitive data which can be produced via mock generation.
- The run has not progressed past the planning stage, or did not create a plan successfully.
- The run progressed past the planning stage prior to July 23, 2021. Prior to this date, HCP Terraform only kept JSON plans for 7 days.
If a plan cannot have its mock data exported due to any of these reasons, the Download Sentinel mocks button within the plan status section of the UI will not be visible.
Note: Only a successful plan is required for mock generation. Sentinel can still generate the data if apply or policy checks fail.