diff --git a/runkit/decorate.go b/runkit/decorate.go
index b6d7085..268a9a8 100644
--- a/runkit/decorate.go
+++ b/runkit/decorate.go
@@ -17,28 +17,35 @@ import (
 
 func Decorate(ctx context.Context, src, dest string, runxConfig, runxDoc []byte) error {
 	var (
-		index                    v1.ImageIndex
-		desc                     *remote.Descriptor
-		remoteOpts               = registry.WithOptions(ctx, nil)
-		ref, _                   = name.ParseReference(src)
-		destRef, _               = name.ParseReference(dest)
-		runxImage, runxDesc, err = Image(runxConfig, runxDoc)
+		err          error
+		index        v1.ImageIndex
+		desc         *remote.Descriptor
+		remoteOpts   = registry.WithOptions(ctx, nil)
+		ref, destRef name.Reference
+		runxImage    v1.Image
+		runxDesc     *v1.Descriptor
 	)
 
-	if err != nil {
+	if ref, err = name.ParseReference(src); err != nil {
+		return err
+	}
+	if destRef, err = name.ParseReference(dest); err != nil {
+		return err
+	}
+	if runxImage, runxDesc, err = Image(runxConfig, runxDoc); err != nil {
 		return fmt.Errorf("could not create runx image: %w", err)
 	}
 
 	if src == "scratch" {
 		index = // create a manifest
-		mutate.AppendManifests(
-			// as an index
-			mutate.IndexMediaType(empty.Index, types.OCIImageIndex),
-			// and the new runx image
-			mutate.IndexAddendum{
-				Add:        runxImage,
-				Descriptor: *runxDesc,
-			})
+			mutate.AppendManifests(
+				// as an index
+				mutate.IndexMediaType(empty.Index, types.OCIImageIndex),
+				// and the new runx image
+				mutate.IndexAddendum{
+					Add:        runxImage,
+					Descriptor: *runxDesc,
+				})
 	} else {
 		desc, err = remote.Get(ref, remoteOpts...)
 		if err != nil {
@@ -55,19 +62,19 @@ func Decorate(ctx context.Context, src, dest string, runxConfig, runxDoc []byte)
 			imgDesc.Platform = configFile.Platform()
 
 			index = // create a manifest
-			mutate.AppendManifests(
-				// as an index
-				mutate.IndexMediaType(empty.Index, types.OCIImageIndex),
-				// with the referenced image
-				mutate.IndexAddendum{
-					Add:        img,
-					Descriptor: imgDesc,
-				},
-				// and the new runx image
-				mutate.IndexAddendum{
-					Add:        runxImage,
-					Descriptor: *runxDesc,
-				})
+				mutate.AppendManifests(
+					// as an index
+					mutate.IndexMediaType(empty.Index, types.OCIImageIndex),
+					// with the referenced image
+					mutate.IndexAddendum{
+						Add:        img,
+						Descriptor: imgDesc,
+					},
+					// and the new runx image
+					mutate.IndexAddendum{
+						Add:        runxImage,
+						Descriptor: *runxDesc,
+					})
 		} else if desc.MediaType.IsIndex() {
 			index, err = remote.Index(ref, remoteOpts...)
 			if err != nil {
diff --git a/runkit/runkit_test.go b/runkit/runkit_test.go
new file mode 100644
index 0000000..4f10ce8
--- /dev/null
+++ b/runkit/runkit_test.go
@@ -0,0 +1,82 @@
+package runkit
+
+import (
+	"context"
+	"io"
+	"log"
+	"net/http/httptest"
+	"net/url"
+	"strings"
+	"testing"
+
+	"github.com/google/go-containerregistry/pkg/registry"
+)
+
+func TestDecorateReferences(t *testing.T) {
+	t.Run("wrong input source", func(t *testing.T) {
+		t.Parallel()
+		reg := newTestRegistry(t)
+		imgDest := reg + "/test-references:" + strings.ReplaceAll(t.Name(), "/", "_")
+		err := Decorate(context.TODO(), "not/a:valid/reference", imgDest, []byte("default: run"), nil)
+		if err == nil {
+			t.Error("should raise an error about invalid reference")
+		} else if !strings.Contains(err.Error(), "could not parse reference") {
+			t.Error("should raise an error about invalid reference")
+		}
+	})
+
+	t.Run("wrong input source", func(t *testing.T) {
+		t.Parallel()
+		err := Decorate(context.TODO(), "scratch", "not/a:valid/reference", nil, nil)
+		if err == nil {
+			t.Error("should raise an error about invalid reference")
+		} else if !strings.Contains(err.Error(), "could not parse reference") {
+			t.Error("should raise an error about invalid reference")
+		}
+	})
+}
+
+func TestDecorateFromScratch(t *testing.T) {
+	t.Run("readme only", func(t *testing.T) {
+		t.Parallel()
+		reg := newTestRegistry(t)
+		imgDest := reg + "/test-scratch:" + strings.ReplaceAll(t.Name(), "/", "_")
+		err := Decorate(context.TODO(), "scratch", imgDest, nil, []byte("# Docker Runx\n\n**Hello!**"))
+		if err != nil {
+			t.Error(err)
+		}
+	})
+
+	t.Run("config only", func(t *testing.T) {
+		t.Parallel()
+		reg := newTestRegistry(t)
+		imgDest := reg + "/test-scratch:" + strings.ReplaceAll(t.Name(), "/", "_")
+		err := Decorate(context.TODO(), "scratch", imgDest, []byte("default: run"), nil)
+		if err != nil {
+			t.Error(err)
+		}
+	})
+
+	t.Run("both", func(t *testing.T) {
+		t.Parallel()
+		reg := newTestRegistry(t)
+		imgDest := reg + "/test-scratch:" + strings.ReplaceAll(t.Name(), "/", "_")
+		err := Decorate(context.TODO(), "scratch", imgDest, []byte("default: run"), []byte("# Docker Runx\n\n**Hello!**"))
+		if err != nil {
+			t.Error(err)
+		}
+	})
+}
+
+func newTestRegistry(t *testing.T) string {
+	s := httptest.NewServer(
+		registry.New(
+			registry.WithBlobHandler(registry.NewInMemoryBlobHandler()),
+			registry.Logger(log.New(io.Discard, "", log.Ldate))))
+	t.Cleanup(s.Close)
+	u, err := url.Parse(s.URL)
+	if err != nil {
+		t.Fatal(err)
+	}
+	return u.Host
+}