Custom Plan Checks

The package plancheck also provides the PlanCheck interface, which can be implemented for a custom plan check.

The plancheck.CheckPlanRequest contains the current plan file, parsed by the terraform-json package.

Here is an example implementation of a plan check that asserts that every resource change is a no-op, aka, an empty plan:

package example_testimport (    "context"    "fmt"    "github.com/hashicorp/terraform-plugin-testing/plancheck")var _ plancheck.PlanCheck = expectEmptyPlan{}type expectEmptyPlan struct{}func (e expectEmptyPlan) CheckPlan(ctx context.Context, req plancheck.CheckPlanRequest, resp *plancheck.CheckPlanResponse) {    var result error    for _, rc := range req.Plan.ResourceChanges {        if !rc.Change.Actions.NoOp() {            result = errors.Join(result, fmt.Errorf("expected empty plan, but %s has planned action(s): %v", rc.Address, rc.Change.Actions))        }    }    resp.Error = result}func ExpectEmptyPlan() plancheck.PlanCheck {    return expectEmptyPlan{}}

And example usage:

package example_testimport (    "context"    "errors"    "fmt"    "testing"    "github.com/hashicorp/terraform-plugin-testing/helper/resource"    "github.com/hashicorp/terraform-plugin-testing/plancheck")func Test_CustomPlanCheck_ExpectEmptyPlan(t *testing.T) {    t.Parallel()    resource.Test(t, resource.TestCase{        ExternalProviders: map[string]resource.ExternalProvider{            "random": {                Source: "registry.terraform.io/hashicorp/random",            },        },        Steps: []resource.TestStep{            {                Config: `resource "random_string" "one" {                    length = 16                }`,            },            {                Config: `resource "random_string" "one" {                    length = 16                }`,                ConfigPlanChecks: resource.ConfigPlanChecks{                    PreApply: []plancheck.PlanCheck{                        ExpectEmptyPlan(),                    },                },            },        },    })}