Proposal: Allow using `Computed` values from `statecheck.StateCheck` in subsequent `knownvalue.Check`

[gdavison]

terraform-plugin-testing version

github.com/hashicorp/terraform-plugin-testing v1.14.0-beta.1

Use cases

When testing List Resources, to fully validate, e.g. that a Resource Identity is present in the results, the full Resource Identity is needed. However, attributes in the Resource Identity may be Computed, and therefore must be retrieved from the resource itself.

Proposal

Add a struct, inspired by statecheck.CompareValue that can be initialized using a statecheck.StateCheck and then used as a knownvalue.Check.

I'm not sure which package this would fit best in, so in the example, I'll use some_pkg.

For example:

func TestExample(t *testing.T) {
  id := some_pkg.StateValue()

  // ...

  Steps: []resource.TestStep{
    {
      // ...
      ConfigStateChecks: []statecheck.StateCheck{
        id.GetStateValue(resourceName, tfjsonpath.New("id"),
      },
    },
    {
      // ...
      Query: true,
      QueryResultChecks: []querycheck.QueryResultCheck{
        querycheck.ExpectIdentity("aws_vpc.test", map[string]knownvalue.Check{
          "account_id": tfknownvalue.AccountID(),
          "region":    knownvalue.StringExact(acctest.Region()),
          "id":        id.Value(),
        }),
      },
    },
  })
}

I have a working implementation in hashicorp/terraform-provider-aws#44609