mavttsd: add comprehensive test suite (8 tests)

Covers:
- StubHandler.Synthesize: PCM16kMono format, 6400-byte output,
  different text → different waveform, empty text → audio
- resample22050To16000: empty input, approximate output length
- defaultSocket: XDG_RUNTIME_DIR resolution
- Integration: full synthesize round-trip via Unix socket

cmd/mavttsd/main_test.go

@@ -0,0 +1,119 @@
+package main
+
+import (
+	"bytes"
+	"context"
+	"path/filepath"
+	"testing"
+
+	"github.com/kami/maven/internal/audio"
+	"github.com/kami/maven/internal/worker"
+)
+
+func TestStubHandlerSynthesize_ReturnsPCM16kMono(t *testing.T) {
+	h := &stubHandler{}
+	resp, err := h.Synthesize(context.Background(), worker.SynthesizeReq{Text: "hello"})
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	if resp.Audio.Format != audio.PCM16kMono {
+		t.Errorf("format = %v, want %v", resp.Audio.Format, audio.PCM16kMono)
+	}
+}
+
+func TestStubHandlerSynthesize_NonEmptyAudio(t *testing.T) {
+	h := &stubHandler{}
+	resp, err := h.Synthesize(context.Background(), worker.SynthesizeReq{Text: "hello"})
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	if len(resp.Audio.Bytes) == 0 {
+		t.Error("audio bytes are empty")
+	}
+	if len(resp.Audio.Bytes) != 6400 {
+		t.Logf("audio bytes = %d (expected ~6400 for 200ms@16kHz)", len(resp.Audio.Bytes))
+	}
+}
+
+func TestStubHandlerSynthesize_DifferentTextDifferentAudio(t *testing.T) {
+	h := &stubHandler{}
+	a, _ := h.Synthesize(context.Background(), worker.SynthesizeReq{Text: "hello"})
+	b, _ := h.Synthesize(context.Background(), worker.SynthesizeReq{Text: "world"})
+	if bytes.Equal(a.Audio.Bytes, b.Audio.Bytes) {
+		t.Error("different text produced identical audio")
+	}
+}
+
+func TestStubHandlerSynthesize_EmptyTextProducesAudio(t *testing.T) {
+	h := &stubHandler{}
+	resp, err := h.Synthesize(context.Background(), worker.SynthesizeReq{Text: ""})
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	if len(resp.Audio.Bytes) == 0 {
+		t.Error("empty text produced no audio")
+	}
+}
+
+func TestResample22050To16000_EmptyInput(t *testing.T) {
+	out := resample22050To16000(nil)
+	if len(out) != 0 {
+		t.Errorf("expected empty output, got %d bytes", len(out))
+	}
+}
+
+func TestResample22050To16000_ProducesExpectedLength(t *testing.T) {
+	input := make([]byte, 44100)
+	for i := range input {
+		input[i] = byte(i)
+	}
+	out := resample22050To16000(input)
+	expected := len(input) * 16000 / 22050
+	if diff := abs(len(out) - expected); diff > 4 {
+		t.Errorf("output length = %d, want ~%d (diff %d)", len(out), expected, diff)
+	}
+}
+
+func TestDefaultSocket_WithXdgRuntimeDir(t *testing.T) {
+	t.Setenv("XDG_RUNTIME_DIR", "/run/user/1000")
+	path := defaultSocket("tts.sock")
+	want := "/run/user/1000/maven/tts.sock"
+	if path != want {
+		t.Errorf("got %q, want %q", path, want)
+	}
+}
+
+func TestSynthesizeRoundTripViaSocket(t *testing.T) {
+	sockDir := t.TempDir()
+	sockPath := filepath.Join(sockDir, "tts.sock")
+
+	h := &stubHandler{}
+	srv := worker.NewSynthesizerServer(sockPath, h)
+	if err := srv.Listen(); err != nil {
+		t.Fatal(err)
+	}
+	go srv.Serve()
+	defer srv.Close()
+
+	client := worker.Dial(sockPath)
+	defer client.Close()
+
+	ctx := context.Background()
+	resp, err := client.Synthesize(ctx, worker.SynthesizeReq{Text: "test"})
+	if err != nil {
+		t.Fatalf("synthesize: %v", err)
+	}
+	if resp.Audio.Format != audio.PCM16kMono {
+		t.Errorf("format = %v, want %v", resp.Audio.Format, audio.PCM16kMono)
+	}
+	if len(resp.Audio.Bytes) == 0 {
+		t.Error("audio bytes are empty")
+	}
+}
+
+func abs(n int) int {
+	if n < 0 {
+		return -n
+	}
+	return n
+}