Add tests for ImageFetcher

[#90]

Signed-off-by: Danny Joyce <[email protected]>
Signed-off-by: Andrew Meyer <[email protected]>

image_fetcher.go

@@ -25,52 +25,22 @@ func (f *ImageFetcher) FetchUpdatedLocalImage(ctx context.Context, imageName str
 		return nil, err
 	}
 
-	found, err := expectedImage.Found()
-	if err != nil {
+	if found, err := expectedImage.Found(); err != nil {
 		return nil, err
-	}
-
-	if found {
+	} else if found {
 		err = f.Docker.PullImage(ctx, imageName, stdout)
 		if err != nil {
 			return nil, err
 		}
-
-	}
-	expectedImage, err = f.FetchLocalImage(imageName)
-	if err != nil {
-		return nil, err
 	}
 
-	return expectedImage, nil
+	return f.FetchLocalImage(imageName)
 }
 
 func (f *ImageFetcher) FetchLocalImage(imageName string) (image.Image, error) {
-	expectedImage, err := f.Factory.NewLocal(imageName)
-
-	if err != nil {
-		return nil, err
-	}
-
-	found, err := expectedImage.Found()
-
-	if err != nil {
-		return nil, err
-	}
-
-	if !found {
-		return nil, nil
-	}
-
-	return expectedImage, nil
+	return f.Factory.NewLocal(imageName)
 }
 
 func (f *ImageFetcher) FetchRemoteImage(imageName string) (image.Image, error) {
-	expectedImage, err := f.Factory.NewRemote(imageName)
-
-	if err != nil {
-		return nil, err
-	}
-
-	return expectedImage, nil
+	return f.Factory.NewRemote(imageName)
 }

image_fetcher_test.go

@@ -0,0 +1,104 @@
+package pack_test
+
+import (
+	"context"
+	"io/ioutil"
+	"testing"
+
+	"github.com/fatih/color"
+	"github.com/golang/mock/gomock"
+	"github.com/sclevine/spec"
+	"github.com/sclevine/spec/report"
+
+	"github.com/buildpack/pack"
+	"github.com/buildpack/pack/mocks"
+	h "github.com/buildpack/pack/testhelpers"
+)
+
+func TestImageFetcher(t *testing.T) {
+	color.NoColor = true
+	spec.Run(t, "ImageFetcher", testImageFetcher, spec.Report(report.Terminal{}))
+}
+
+func testImageFetcher(t *testing.T, when spec.G, it spec.S) {
+	var (
+		fetcher          pack.ImageFetcher
+		mockController   *gomock.Controller
+		mockImageFactory *mocks.MockImageFactory
+		mockRemoteImage  *mocks.MockImage
+		mockLocalImage   *mocks.MockImage
+		mockDocker       *mocks.MockDocker
+	)
+
+	it.Before(func() {
+		mockController = gomock.NewController(t)
+		mockImageFactory = mocks.NewMockImageFactory(mockController)
+		mockRemoteImage = mocks.NewMockImage(mockController)
+		mockLocalImage = mocks.NewMockImage(mockController)
+		mockDocker = mocks.NewMockDocker(mockController)
+		fetcher = pack.ImageFetcher{
+			Docker:  mockDocker,
+			Factory: mockImageFactory,
+		}
+	})
+
+	it.After(func() {
+		mockController.Finish()
+	})
+
+	when("#FetchUpdatedLocalImage", func() {
+		when("remote image exists", func() {
+			it.Before(func() {
+				mockRemoteImage.EXPECT().Found().Return(true, nil)
+				mockImageFactory.EXPECT().NewRemote("some/image").Return(mockRemoteImage, nil)
+				mockImageFactory.EXPECT().NewLocal("some/image").Return(mockLocalImage, nil)
+			})
+
+			it("pulls remote image", func() {
+				mockDocker.EXPECT().PullImage(gomock.Any(), "some/image", gomock.Any())
+				img, err := fetcher.FetchUpdatedLocalImage(context.TODO(), "some/image", ioutil.Discard)
+				h.AssertNil(t, err)
+				h.AssertSameInstance(t, img, mockLocalImage)
+			})
+		})
+
+		when("remote image does not exist", func() {
+			it.Before(func() {
+				mockRemoteImage.EXPECT().Found().Return(false, nil)
+				mockImageFactory.EXPECT().NewRemote("some/image").Return(mockRemoteImage, nil)
+				mockImageFactory.EXPECT().NewLocal("some/image").Return(mockLocalImage, nil)
+			})
+
+			it("skips pulling image", func() {
+				mockDocker.EXPECT().PullImage(gomock.Any(), gomock.Any(), gomock.Any()).Times(0)
+				img, err := fetcher.FetchUpdatedLocalImage(context.TODO(), "some/image", ioutil.Discard)
+				h.AssertNil(t, err)
+				h.AssertSameInstance(t, img, mockLocalImage)
+			})
+		})
+	})
+
+	when("#FetchLocalImage", func() {
+		it.Before(func() {
+			mockImageFactory.EXPECT().NewLocal("some/image").Return(mockLocalImage, nil)
+		})
+
+		it("returns local image", func() {
+			img, err := fetcher.FetchLocalImage("some/image")
+			h.AssertNil(t, err)
+			h.AssertSameInstance(t, img, mockLocalImage)
+		})
+	})
+
+	when("#FetchRemoteImage", func() {
+		it.Before(func() {
+			mockImageFactory.EXPECT().NewRemote("some/image").Return(mockRemoteImage, nil)
+		})
+
+		it("returns remote image", func() {
+			img, err := fetcher.FetchRemoteImage("some/image")
+			h.AssertNil(t, err)
+			h.AssertSameInstance(t, img, mockRemoteImage)
+		})
+	})
+}