test(02-01): add failing tests for synth config, oscillator, and layer

- TestAllClassesHaveConfig, TestFrequenciesInRange, TestFrequenciesUnique
- TestHarmonicsNonEmpty, TestPanPositionsInRange
- TestOscillatorAdvance, TestOscillatorPhaseWrap, TestOscillatorDistinctFreqs
- TestEMAAmplitudeRise, TestEMAAmplitudeDecay, TestWhisperFloor, TestWhisperFloorNotSeenIsZero

synth/layer_test.go

@@ -0,0 +1,88 @@
+package synth_test
+
+import (
+	"testing"
+
+	"github.com/netsynth/netsynth/synth"
+)
+
+func TestEMAAmplitudeRise(t *testing.T) {
+	cfg2 := synth.FreqConfig{
+		BaseHz:    440.0,
+		Harmonics: []synth.HarmonicDef{{Ratio: 1, Amplitude: 1.0}},
+		Pan:       0.0,
+	}
+	layer := synth.NewLayer(cfg2, synth.SampleRate, 1.0)
+
+	// Force the layer to have been seen and set target to 1.0
+	layer.UpdateTarget(100, 100)
+
+	// After 1 second (SampleRate samples) with tau=1.0, currentAmp should be > 0.5
+	// EMA: after tau seconds, amplitude reaches ~63% of target
+	for i := 0; i < synth.SampleRate; i++ {
+		layer.AdvanceSample()
+	}
+	if layer.CurrentAmp() <= 0.5 {
+		t.Errorf("expected currentAmp > 0.5 after 1 second rise, got %.4f", layer.CurrentAmp())
+	}
+}
+
+func TestEMAAmplitudeDecay(t *testing.T) {
+	cfg := synth.FreqConfig{
+		BaseHz:    440.0,
+		Harmonics: []synth.HarmonicDef{{Ratio: 1, Amplitude: 1.0}},
+		Pan:       0.0,
+	}
+	layer := synth.NewLayer(cfg, synth.SampleRate, 1.0)
+
+	// Set up: layer has been seen (currentAmp starts at 1.0) and target is whisper floor
+	// We'll manually prime by updating target with 100/100 first then re-route to whisper
+	layer.UpdateTarget(100, 100) // mark as seen, target=1.0
+	// Force currentAmp to 1.0 by running a few cycles at target 1.0
+	for i := 0; i < synth.SampleRate*3; i++ {
+		layer.AdvanceSample()
+	}
+	// Now decay: set count=0 (whisper floor kicks in)
+	layer.UpdateTarget(0, 100)
+	// After 1 second, currentAmp should be < 0.5
+	for i := 0; i < synth.SampleRate; i++ {
+		layer.AdvanceSample()
+	}
+	if layer.CurrentAmp() >= 0.5 {
+		t.Errorf("expected currentAmp < 0.5 after 1 second decay, got %.4f", layer.CurrentAmp())
+	}
+}
+
+func TestWhisperFloor(t *testing.T) {
+	cfg := synth.FreqConfig{
+		BaseHz:    440.0,
+		Harmonics: []synth.HarmonicDef{{Ratio: 1, Amplitude: 1.0}},
+		Pan:       0.0,
+	}
+	layer := synth.NewLayer(cfg, synth.SampleRate, 1.0)
+
+	// Mark layer as seen by passing count=1, then set count=0
+	layer.UpdateTarget(1, 100)
+	layer.UpdateTarget(0, 100)
+
+	// Target should be whisper floor (not zero) because seen=true
+	if layer.TargetAmp() < synth.WhisperFloor {
+		t.Errorf("expected targetAmp >= WhisperFloor (%.2f) for seen layer at zero count, got %.4f",
+			synth.WhisperFloor, layer.TargetAmp())
+	}
+}
+
+func TestWhisperFloorNotSeenIsZero(t *testing.T) {
+	cfg := synth.FreqConfig{
+		BaseHz:    440.0,
+		Harmonics: []synth.HarmonicDef{{Ratio: 1, Amplitude: 1.0}},
+		Pan:       0.0,
+	}
+	layer := synth.NewLayer(cfg, synth.SampleRate, 1.0)
+
+	// Never seen — UpdateTarget with zero count
+	layer.UpdateTarget(0, 100)
+	if layer.TargetAmp() != 0.0 {
+		t.Errorf("expected targetAmp == 0.0 for unseen layer, got %.4f", layer.TargetAmp())
+	}
+}