Support injecting errors for FakeImageService

We want `FakeImageService` to support injecting errors similar to
`FakeRuntimeService`. These injected errors will be returned on the next
call to the given function.

We will use the ability to inject errors to more thoroughly test
the image management component of the KubeRuntimeManager.

staging/src/k8s.io/cri-api/pkg/apis/testing/fake_image_service.go

@@ -30,6 +30,7 @@ type FakeImageService struct {
 
 	FakeImageSize uint64
 	Called        []string
+	Errors        map[string][]error
 	Images        map[string]*runtimeapi.Image
 
 	pulledImages []*pulledImage
@@ -87,11 +88,34 @@ func stringInSlice(s string, list []string) bool {
 	return false
 }
 
+func (r *FakeImageService) InjectError(f string, err error) {
+	r.Lock()
+	defer r.Unlock()
+	r.Errors[f] = append(r.Errors[f], err)
+}
+
+// caller of popError must grab a lock.
+func (r *FakeImageService) popError(f string) error {
+	if r.Errors == nil {
+		return nil
+	}
+	errs := r.Errors[f]
+	if len(errs) == 0 {
+		return nil
+	}
+	err, errs := errs[0], errs[1:]
+	r.Errors[f] = errs
+	return err
+}
+
 func (r *FakeImageService) ListImages(filter *runtimeapi.ImageFilter) ([]*runtimeapi.Image, error) {
 	r.Lock()
 	defer r.Unlock()
 
 	r.Called = append(r.Called, "ListImages")
+	if err := r.popError("ListImages"); err != nil {
+		return nil, err
+	}
 
 	images := make([]*runtimeapi.Image, 0)
 	for _, img := range r.Images {
@@ -111,6 +135,9 @@ func (r *FakeImageService) ImageStatus(image *runtimeapi.ImageSpec) (*runtimeapi
 	defer r.Unlock()
 
 	r.Called = append(r.Called, "ImageStatus")
+	if err := r.popError("ImageStatus"); err != nil {
+		return nil, err
+	}
 
 	return r.Images[image.Image], nil
 }
@@ -120,6 +147,9 @@ func (r *FakeImageService) PullImage(image *runtimeapi.ImageSpec, auth *runtimea
 	defer r.Unlock()
 
 	r.Called = append(r.Called, "PullImage")
+	if err := r.popError("PullImage"); err != nil {
+		return "", err
+	}
 
 	r.pulledImages = append(r.pulledImages, &pulledImage{imageSpec: image, authConfig: auth})
 	// ImageID should be randomized for real container runtime, but here just use
@@ -137,6 +167,9 @@ func (r *FakeImageService) RemoveImage(image *runtimeapi.ImageSpec) error {
 	defer r.Unlock()
 
 	r.Called = append(r.Called, "RemoveImage")
+	if err := r.popError("RemoveImage"); err != nil {
+		return err
+	}
 
 	// Remove the image
 	delete(r.Images, image.Image)
@@ -150,6 +183,9 @@ func (r *FakeImageService) ImageFsInfo() ([]*runtimeapi.FilesystemUsage, error)
 	defer r.Unlock()
 
 	r.Called = append(r.Called, "ImageFsInfo")
+	if err := r.popError("ImageFsInfo"); err != nil {
+		return nil, err
+	}
 
 	return r.FakeFilesystemUsage, nil
 }