diff --git a/cmd/run.go b/cmd/run.go
index a805eb7..cbe73d5 100644
--- a/cmd/run.go
+++ b/cmd/run.go
@@ -51,6 +51,6 @@ func main() {
 	fmt.Println(err)
 	out, err := os.Create("./collage.jpg")
 	fmt.Println(err)
-	err = collage.Make(req, os.DirFS("."), out)
+	err = collage.Make(&req, os.DirFS("."), out)
 	fmt.Println(err)
 }
diff --git a/collage/collage.go b/collage/collage.go
index 5197790..1f5420e 100644
--- a/collage/collage.go
+++ b/collage/collage.go
@@ -48,7 +48,7 @@ type Request struct {
 	Photos          []Photo   `json:"photos"`
 }
 
-func Make(req Request, source fs.FS, output io.Writer) error {
+func Make(req *Request, source fs.FS, output io.Writer) error {
 	rec := image.Rect(0, 0, int(req.Aspect.Width), int(req.Aspect.Height))
 	canvas := image.NewRGBA64(rec)
 	white := color.RGBA{255, 255, 255, 255}
diff --git a/collage/collage_test.go b/collage/collage_test.go
index 5971111..ef4a3c0 100644
--- a/collage/collage_test.go
+++ b/collage/collage_test.go
@@ -67,7 +67,7 @@ func TestMake(t *testing.T) {
 		t.Fatalf("failed to create ouput image file %v", err)
 	}
 
-	err = Make(req, testDataFS, out)
+	err = Make(&req, testDataFS, out)
 	if err != nil {
 		t.Fatalf("failed to make collage %v", err)
 	}
diff --git a/main.go b/main.go
index 6acc19e..ab40a46 100644
--- a/main.go
+++ b/main.go
@@ -20,13 +20,15 @@ import (
 )
 
 var (
-	imagesDir   string
-	collageDir  string
-	localAssets bool
-)
+	imagesDir      string
+	collageDir     string
+	localAssets    bool
+	collageNameGen *nameGen
+	imagesDirFs    fs.FS
 
-//go:embed web/*
-var webFS embed.FS
+	// go:embed web/*
+	webFS embed.FS
+)
 
 func main() {
 	flag.StringVar(&imagesDir, "images-dir", "images", "Sets the images dir")
@@ -34,8 +36,9 @@ func main() {
 	flag.BoolVar(&localAssets, "local-assets", false, "Serve local assets for testing")
 
 	flag.Parse()
-	nameGen := NewNameGen()
-	imagesDirFs := os.DirFS(imagesDir)
+
+	collageNameGen = NewNameGen()
+	imagesDirFs = os.DirFS(imagesDir)
 	imagesURLPath := "images"
 	collagesPath := "collages"
 
@@ -67,19 +70,18 @@ func main() {
 		body, err := io.ReadAll(r.Body)
 		if err != nil {
 			slog.Error("failed to read request body", "error", err)
+			w.WriteHeader(http.StatusInternalServerError)
 			return
 		}
 		if err := json.Unmarshal(body, &collageReq); err != nil {
 			slog.Error("failed to unmarshal json request", "error", err)
+			w.WriteHeader(http.StatusInternalServerError)
 			return
 		}
-		collageFile := fmt.Sprintf("collage-%s.jpg", nameGen.Next())
-		out, err := os.Create(path.Join(collageDir, collageFile))
+		collageFile, err := MakeCollage(&collageReq)
 		if err != nil {
-			slog.Error("failed to create collage output file", "error", err)
-		}
-		if err := collage.Make(collageReq, imagesDirFs, out); err != nil {
 			slog.Error("failed to make collage", "error", err)
+			w.WriteHeader(http.StatusInternalServerError)
 			return
 		}
 		w.Write([]byte(collageFile))
@@ -116,4 +118,17 @@ func (n *nameGen) Next() string {
 	return fmt.Sprintf("%s-%d", n.prefix, n.counter.Add(1))
 }
 
+func MakeCollage(req *collage.Request) (string, error) {
+	collageFile := fmt.Sprintf("collage-%s.jpg", collageNameGen.Next())
+	out, err := os.Create(path.Join(collageDir, collageFile))
+	if err != nil {
+		return "", fmt.Errorf("failed to create collage output file, err: %w", err)
+		// slog.Error("failed to create collage output file", "error", err)
+	}
+	if err := collage.Make(req, imagesDirFs, out); err != nil {
+		return "", fmt.Errorf("failed to make collage, err: %w", err)
+	}
+	return collageFile, nil
+}
+
 // curl -D - --json @req.json http://localhost:8767/make-collage
diff --git a/main_test.go b/main_test.go
index 34e9f73..40a8d5c 100644
--- a/main_test.go
+++ b/main_test.go
@@ -6,5 +6,4 @@ func TestNameGen(t *testing.T) {
 	g := NewNameGen()
 	t.Logf("next id: %s", g.Next())
 	t.Logf("next id: %s", g.Next())
-	t.Fail()
 }