sfx-maker: sfxc - sfxr-style .sfx text presets -> 16-bit WAV synthesis

- waves: square (duty), saw, sine, triangle, pitched noise (seeded, deterministic)
- envelope attack/sustain/decay, freq slide, vibrato, arpeggio jump,
  one-pole low/high-pass filters, clamped output
- presets blip/coin/explosion/hurt/jump/laser/powerup with seeded variants;
  preset writes editable .sfx or renders .wav directly
- go tests: parse/validate, determinism, per-preset RMS, WAV header roundtrip

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01MmdG9GqfSWCzts7AkDwRDh

sfx-maker/sfx/sfx_test.go

@@ -0,0 +1,164 @@
+package sfx
+
+import (
+	"bytes"
+	"math"
+	"strings"
+	"testing"
+)
+
+func TestParseAndValidate(t *testing.T) {
+	src := `
+# a jump
+sfx: jump
+wave: square
+freq: 330
+freq-slide: 900
+attack: 0.01
+sustain: 0.08
+decay: 0.18
+duty: 0.4
+`
+	p, err := Parse(strings.NewReader(src))
+	if err != nil {
+		t.Fatal(err)
+	}
+	if p.Name != "jump" || p.Wave != "square" || p.Freq != 330 || p.Duty != 0.4 {
+		t.Errorf("parsed wrong: %+v", p)
+	}
+	if math.Abs(p.Duration()-0.27) > 1e-9 {
+		t.Errorf("duration = %g, want 0.27", p.Duration())
+	}
+}
+
+func TestParseErrors(t *testing.T) {
+	cases := map[string]string{
+		"unknown key":  "wat: 3\n",
+		"bad wave":     "wave: wobble\n",
+		"bad value":    "freq: abc\n",
+		"zero length":  "attack: 0\nsustain: 0\ndecay: 0\n",
+		"volume range": "volume: 2\n",
+		"duty range":   "duty: 0.99\n",
+	}
+	for name, src := range cases {
+		if _, err := Parse(strings.NewReader(src)); err == nil {
+			t.Errorf("%s: expected error", name)
+		}
+	}
+}
+
+func TestRenderBasics(t *testing.T) {
+	p := Defaults()
+	p.Wave = "sine"
+	p.Attack, p.Sustain, p.Decay = 0.01, 0.05, 0.05
+	samples := Render(&p)
+	want := int(0.11 * 44100)
+	if len(samples) != want {
+		t.Errorf("samples = %d, want %d", len(samples), want)
+	}
+	var peak float64
+	for _, s := range samples {
+		if math.Abs(s) > peak {
+			peak = math.Abs(s)
+		}
+		if s > 1 || s < -1 {
+			t.Fatalf("sample %g out of range", s)
+		}
+	}
+	if peak < 0.5 {
+		t.Errorf("peak %g suspiciously quiet", peak)
+	}
+	// end of decay should be silent-ish
+	tail := samples[len(samples)-10:]
+	for _, s := range tail {
+		if math.Abs(s) > 0.1 {
+			t.Errorf("tail sample %g not decayed", s)
+		}
+	}
+}
+
+func TestRenderDeterministic(t *testing.T) {
+	p := Defaults()
+	p.Wave = "noise"
+	p.Seed = 42
+	a := Render(&p)
+	b := Render(&p)
+	for i := range a {
+		if a[i] != b[i] {
+			t.Fatalf("noise render not deterministic at sample %d", i)
+		}
+	}
+}
+
+func TestAllWavesAndPresets(t *testing.T) {
+	for _, w := range []string{"square", "saw", "sine", "triangle", "noise"} {
+		p := Defaults()
+		p.Wave = w
+		if s := Render(&p); len(s) == 0 {
+			t.Errorf("wave %s rendered nothing", w)
+		}
+	}
+	for _, name := range []string{"blip", "coin", "explosion", "hurt", "jump", "laser", "powerup"} {
+		p, err := Preset(name, 0)
+		if err != nil {
+			t.Errorf("preset %s: %v", name, err)
+			continue
+		}
+		s := Render(p)
+		var sum float64
+		for _, v := range s {
+			sum += v * v
+		}
+		rms := math.Sqrt(sum / float64(len(s)))
+		if rms < 0.01 {
+			t.Errorf("preset %s is nearly silent (rms %g)", name, rms)
+		}
+		// variants stay valid
+		if _, err := Preset(name, 7); err != nil {
+			t.Errorf("preset %s seed 7: %v", name, err)
+		}
+	}
+	if _, err := Preset("nope", 0); err == nil {
+		t.Error("unknown preset should error")
+	}
+}
+
+func TestWAVRoundTrip(t *testing.T) {
+	p := Defaults()
+	samples := Render(&p)
+	var buf bytes.Buffer
+	if err := WriteWAV(&buf, samples, p.SampleRate); err != nil {
+		t.Fatal(err)
+	}
+	sr, bits, ch, dataBytes, err := ReadWAVHeader(&buf)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if sr != 44100 || bits != 16 || ch != 1 {
+		t.Errorf("header: sr=%d bits=%d ch=%d", sr, bits, ch)
+	}
+	if dataBytes != len(samples)*2 {
+		t.Errorf("dataBytes = %d, want %d", dataBytes, len(samples)*2)
+	}
+	if buf.Len() != dataBytes {
+		t.Errorf("body length %d != declared %d", buf.Len(), dataBytes)
+	}
+}
+
+func TestParamsWriteRoundTrip(t *testing.T) {
+	p, err := Preset("coin", 3)
+	if err != nil {
+		t.Fatal(err)
+	}
+	var buf bytes.Buffer
+	if err := p.Write(&buf, "test"); err != nil {
+		t.Fatal(err)
+	}
+	back, err := Parse(&buf)
+	if err != nil {
+		t.Fatalf("re-parse of written .sfx failed: %v\n%s", err, buf.String())
+	}
+	if back.Freq != p.Freq || back.ArpFactor != p.ArpFactor || back.Seed != p.Seed {
+		t.Errorf("roundtrip mismatch: %+v vs %+v", back, p)
+	}
+}