terraform test: fix crash when non-applyable plans are applied

.changes/v1.11/BUG FIXES-20250226-140931.yaml

@@ -0,0 +1,5 @@
+kind: BUG FIXES
+body: '`terraform test`: Fix crash when a run block attempts to cleanup after a non-applyable plan.'
+time: 2025-02-26T14:09:31.83904+01:00
+custom:
+    Issue: "36582"

internal/backend/local/test.go

@@ -937,11 +937,13 @@ func (runner *TestFileRunner) cleanup(file *moduletest.File) {
 	for key, state := range runner.RelevantStates {
 
 		empty := true
-		for _, module := range state.State.Modules {
-			for _, resource := range module.Resources {
-				if resource.Addr.Resource.Mode == addrs.ManagedResourceMode {
-					empty = false
-					break
+		if !state.State.Empty() {
+			for _, module := range state.State.Modules {
+				for _, resource := range module.Resources {
+					if resource.Addr.Resource.Mode == addrs.ManagedResourceMode {
+						empty = false
+						break
+					}
 				}
 			}
 		}

internal/command/test_test.go

@@ -295,6 +295,11 @@ func TestTest_Runs(t *testing.T) {
 			expectedErr: []string{"Test assertion failed", "resource renamed without moved block"},
 			code:        1,
 		},
+		"unapplyable-plan": {
+			expectedOut: []string{"0 passed, 1 failed."},
+			expectedErr: []string{"Cannot apply non-applyable plan"},
+			code:        1,
+		},
 	}
 	for name, tc := range tcs {
 		t.Run(name, func(t *testing.T) {

internal/command/testdata/test/unapplyable-plan/main.tf

@@ -0,0 +1,8 @@
+
+resource "test_resource" "example" {
+  value = "bar"
+}
+
+output "value" {
+  value = test_resource.example.value
+}

internal/command/testdata/test/unapplyable-plan/main.tftest.hcl

@@ -0,0 +1,11 @@
+
+run "test" {
+  command = apply
+  plan_options {
+    mode = refresh-only
+  }
+  assert {
+    condition = test_resource.example.value == "bar"
+    error_message = "wrong value"
+  }
+}