replace the testShutdownHook with a check for Stop

Now that the local backend can be cancelled during plan and refresh, we
don't really need the testShutdownHook. Simplify the tests by just
checking for Stop being called on the provider.

command/apply.go

@@ -171,6 +171,7 @@ func (c *ApplyCommand) Run(args []string) int {
 	// Perform the operation
 	ctx, ctxCancel := context.WithCancel(context.Background())
 	defer ctxCancel()
+
 	op, err := b.Operation(ctx, opReq)
 	if err != nil {
 		c.Ui.Error(fmt.Sprintf("Error starting operation: %s", err))
@@ -183,11 +184,6 @@ func (c *ApplyCommand) Run(args []string) int {
 		// Cancel our context so we can start gracefully exiting
 		ctxCancel()
 
-		// notify tests that the command context was canceled
-		if testShutdownHook != nil {
-			testShutdownHook()
-		}
-
 		// Notify the user
 		c.Ui.Output(outputInterrupt)
 

command/apply_test.go

@@ -825,14 +825,7 @@ func TestApply_refresh(t *testing.T) {
 
 func TestApply_shutdown(t *testing.T) {
 	cancelled := false
-	cancelDone := make(chan struct{})
-	testShutdownHook = func() {
-		cancelled = true
-		close(cancelDone)
-	}
-	defer func() {
-		testShutdownHook = nil
-	}()
+	stopped := make(chan struct{})
 
 	statePath := testTempFile(t)
 	p := testProvider()
@@ -847,6 +840,12 @@ func TestApply_shutdown(t *testing.T) {
 		},
 	}
 
+	p.StopFn = func() error {
+		close(stopped)
+		cancelled = true
+		return nil
+	}
+
 	p.DiffFn = func(
 		*terraform.InstanceInfo,
 		*terraform.InstanceState,
@@ -864,11 +863,11 @@ func TestApply_shutdown(t *testing.T) {
 		*terraform.InstanceState,
 		*terraform.InstanceDiff) (*terraform.InstanceState, error) {
 
+		// only cancel once
 		if !cancelled {
 			shutdownCh <- struct{}{}
-			<-cancelDone
+			<-stopped
 		}
-
 		return &terraform.InstanceState{
 			ID: "foo",
 			Attributes: map[string]string{
@@ -898,10 +897,6 @@ func TestApply_shutdown(t *testing.T) {
 	if state == nil {
 		t.Fatal("state should not be nil")
 	}
-
-	if len(state.RootModule().Resources) != 1 {
-		t.Fatalf("bad: %d", len(state.RootModule().Resources))
-	}
 }
 
 func TestApply_state(t *testing.T) {

command/meta.go

@@ -641,7 +641,3 @@ func isAutoVarFile(path string) bool {
 	return strings.HasSuffix(path, ".auto.tfvars") ||
 		strings.HasSuffix(path, ".auto.tfvars.json")
 }
-
-// testShutdownHook is used by tests to verify that a command context has been
-// canceled
-var testShutdownHook func()

command/plan.go

@@ -118,11 +118,6 @@ func (c *PlanCommand) Run(args []string) int {
 		// Cancel our context so we can start gracefully exiting
 		ctxCancel()
 
-		// notify tests that the command context was canceled
-		if testShutdownHook != nil {
-			testShutdownHook()
-		}
-
 		// Notify the user
 		c.Ui.Output(outputInterrupt)
 

command/plan_test.go

@@ -833,14 +833,7 @@ func TestPlan_detailedExitcode_emptyDiff(t *testing.T) {
 
 func TestPlan_shutdown(t *testing.T) {
 	cancelled := false
-	cancelDone := make(chan struct{})
-	testShutdownHook = func() {
-		cancelled = true
-		close(cancelDone)
-	}
-	defer func() {
-		testShutdownHook = nil
-	}()
+	stopped := make(chan struct{})
 
 	shutdownCh := make(chan struct{})
 	p := testProvider()
@@ -853,6 +846,12 @@ func TestPlan_shutdown(t *testing.T) {
 		},
 	}
 
+	p.StopFn = func() error {
+		close(stopped)
+		cancelled = true
+		return nil
+	}
+
 	p.DiffFn = func(
 		*terraform.InstanceInfo,
 		*terraform.InstanceState,
@@ -860,7 +859,7 @@ func TestPlan_shutdown(t *testing.T) {
 
 		if !cancelled {
 			shutdownCh <- struct{}{}
-			<-cancelDone
+			<-stopped
 		}
 
 		return &terraform.InstanceDiff{