terraform: implement Stop in the mock and shadow

terraform/resource_provider_mock.go

@@ -56,6 +56,9 @@ type MockResourceProvider struct {
 	ReadDataDiffFn                 func(*InstanceInfo, *ResourceConfig) (*InstanceDiff, error)
 	ReadDataDiffReturn             *InstanceDiff
 	ReadDataDiffReturnError        error
+	StopCalled                     bool
+	StopFn                         func() error
+	StopReturnError                error
 	DataSourcesCalled              bool
 	DataSourcesReturn              []DataSource
 	ValidateCalled                 bool
@@ -141,6 +144,18 @@ func (p *MockResourceProvider) Configure(c *ResourceConfig) error {
 	return p.ConfigureReturnError
 }
 
+func (p *MockResourceProvider) Stop() error {
+	p.Lock()
+	defer p.Unlock()
+
+	p.StopCalled = true
+	if p.StopFn != nil {
+		return p.StopFn()
+	}
+
+	return p.StopReturnError
+}
+
 func (p *MockResourceProvider) Apply(
 	info *InstanceInfo,
 	state *InstanceState,

terraform/shadow_resource_provider.go

@@ -107,6 +107,10 @@ func (p *shadowResourceProviderReal) Configure(c *ResourceConfig) error {
 	return err
 }
 
+func (p *shadowResourceProviderReal) Stop() error {
+	return p.ResourceProvider.Stop()
+}
+
 func (p *shadowResourceProviderReal) ValidateResource(
 	t string, c *ResourceConfig) ([]string, []error) {
 	key := t
@@ -441,6 +445,11 @@ func (p *shadowResourceProviderShadow) Configure(c *ResourceConfig) error {
 	return result.Result
 }
 
+// Stop returns immediately.
+func (p *shadowResourceProviderShadow) Stop() error {
+	return nil
+}
+
 func (p *shadowResourceProviderShadow) ValidateResource(t string, c *ResourceConfig) ([]string, []error) {
 	// Unique key
 	key := t