Add Option to use Terraform Configuration in TestStep

[bendbennett]

terraform-plugin-testing version

v1.3.0

Use cases

An individual acceptance test makes use of a TestStep which includes a Config field containing a string representation of Terraform configuration, supplied as either HCL or JSON.

One of the consequences of the Config field using a string is that provider developers can decide on how they pass in Terraform configuration to the tests, for example:

• Usage of raw string syntax (backticks in Go).
• Calling Go standard library functions, such as fmt.Sprintf(), to dynamically generate the string.
• Usage of a Go constant or variable, with a value from either above form.
• Creation a Go function which returns a string (and may or may not take input parameters to make it more dynamic).
• Manually implement a Go function which can read an existing Terraform configuration file.

In all of the above cases except for the last, this can result in varying degrees of consistency in the provider codebase with respect to how Terraform configuration is created and supplied to the tests. Furthermore the usage of a Go string for Terraform configuration means that existing Terraform ecosystem tooling cannot be leveraged. This includes, but is not limited to:

• terraform fmt
• terraform validate
• Editor code syntax highlighting.
• Tooling which can rewrite configurations.
• Cost estimation of running all acceptance tests.
• Collection of data regarding which tests cover a specific resource or data source.

Attempted solutions

Some of the solutions that have been tried are outlined above, such as manually implementing a Go function that can read an existing Terraform configuration file. However, this solution requires implementing by each provider developer and that fact is one of the motivations for this proposal

Proposal

The provider developer experience can be improved by making the development and maintenance of acceptance tests easier through native support of a self-contained Terraform configuration directory. This would require modification of the TestStep struct to include a new ConfigDirectory field which would provide a relative path to a directory containing a Terraform configuration file (*.tf file):

func TestAccExampleThing_basic(t *testing.T) {
    resource.ParallelTest(t, resource.TestCase{
        /* ... */
        Steps: []resource.TestStep{
            {
                ConfigDirectory: "testdata/example_thing/basic",
                Check: /* ... */,
            },
        },
    })
}

To support dynamically updated Terraform configurations, new support for Terraform variable values defined within Go testing code can be injected into the “self-contained” files or directories through the usage of an additional new ConfigVariables field on the TestStep struct:

func TestAccExampleThing_basic(t *testing.T) {
    resource.ParallelTest(t, resource.TestCase{
        /* ... */
        Steps: []resource.TestStep{
            {
                ConfigDirectory: "testdata/example_thing/basic",
                ConfigVariables: map[string]config.Variable{
                    /* ... */

This would allow for the generation of an *.auto.tfvars.json during the execution of an acceptance test, which would then be used within the Terraform configuration file(s) at runtime.

[github-actions]

I'm going to lock this issue because it has been closed for 30 days ⏳. This helps our maintainers find and focus on the active issues.
If you have found a problem that seems similar to this, please open a new issue and complete the issue template so we can capture all the details necessary to investigate further.