Initial GoWallpaper implementation

downloader_test.go

@@ -0,0 +1,52 @@
+package main
+
+import (
+	"context"
+	"image"
+	"image/color"
+	"image/png"
+	"net/http"
+	"net/http/httptest"
+	"os"
+	"path/filepath"
+	"testing"
+)
+
+func TestDownloaderConvertsImageToJPEG(t *testing.T) {
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
+		w.Header().Set("Content-Type", "image/png")
+		img := image.NewRGBA(image.Rect(0, 0, 2, 2))
+		img.Set(0, 0, color.RGBA{R: 255, A: 255})
+		_ = png.Encode(w, img)
+	}))
+	defer server.Close()
+
+	destination := filepath.Join(t.TempDir(), "wallpaper.jpg")
+	if err := newDownloader().download(context.Background(), server.URL, destination); err != nil {
+		t.Fatal(err)
+	}
+	f, err := os.Open(destination)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer f.Close()
+	_, format, err := image.Decode(f)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if format != "jpeg" {
+		t.Fatalf("expected jpeg, got %s", format)
+	}
+}
+
+func TestDownloaderRejectsNonImage(t *testing.T) {
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
+		_, _ = w.Write([]byte("not an image"))
+	}))
+	defer server.Close()
+
+	err := newDownloader().download(context.Background(), server.URL, filepath.Join(t.TempDir(), "wallpaper.jpg"))
+	if err == nil {
+		t.Fatal("expected non-image response to fail")
+	}
+}