diff --git a/internal/app/transcode_test.go b/internal/app/transcode_test.go
new file mode 100644
index 0000000..1669012
--- /dev/null
+++ b/internal/app/transcode_test.go
@@ -0,0 +1,66 @@
+package app
+
+import (
+	"os"
+	"os/exec"
+	"path/filepath"
+	"testing"
+)
+
+func TestFFmpegArgs(t *testing.T) {
+	args := ffmpegArgs("/in/a.flac", "/out/a.mp3", "128k", "Neon Rain", "AI Radio")
+	joined := ""
+	for _, a := range args {
+		joined += a + " "
+	}
+	for _, want := range []string{
+		"-i /in/a.flac",
+		"libmp3lame",
+		"-b:a 128k",
+		"-ar 44100",
+		"-ac 2",
+		"-id3v2_version 3",
+		"-write_id3v1 1",
+		"-metadata title=Neon Rain",
+		"-metadata album=AI Radio",
+		"/out/a.mp3",
+	} {
+		if !contains(joined, want) {
+			t.Fatalf("args missing %q:\n%s", want, joined)
+		}
+	}
+}
+
+func contains(hay, needle string) bool {
+	return len(hay) >= len(needle) && (func() bool {
+		for i := 0; i+len(needle) <= len(hay); i++ {
+			if hay[i:i+len(needle)] == needle {
+				return true
+			}
+		}
+		return false
+	})()
+}
+
+// TestTranscodeReal actually runs ffmpeg if present; skips otherwise.
+func TestTranscodeReal(t *testing.T) {
+	if _, err := exec.LookPath("ffmpeg"); err != nil {
+		t.Skip("ffmpeg not installed")
+	}
+	dir := t.TempDir()
+	src := filepath.Join(dir, "s.flac")
+	// generate a 1s sine flac
+	cmd := exec.Command("ffmpeg", "-y", "-hide_banner", "-loglevel", "error",
+		"-f", "lavfi", "-i", "sine=frequency=440:duration=1", "-c:a", "flac", src)
+	if err := cmd.Run(); err != nil {
+		t.Fatalf("fixture gen: %v", err)
+	}
+	dst := filepath.Join(dir, "s.mp3")
+	if err := Transcode(src, dst, "128k", "Test", "Station"); err != nil {
+		t.Fatalf("Transcode: %v", err)
+	}
+	st, err := os.Stat(dst)
+	if err != nil || st.Size() == 0 {
+		t.Fatal("mp3 not produced")
+	}
+}