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/oscillator_test.go

@@ -0,0 +1,59 @@
+package synth_test
+
+import (
+	"testing"
+
+	"github.com/netsynth/netsynth/synth"
+)
+
+func TestOscillatorAdvance(t *testing.T) {
+	harmonics := []synth.HarmonicDef{{Ratio: 1, Amplitude: 1.0}, {Ratio: 2, Amplitude: 0.5}}
+	osc := synth.NewOscillator(440.0, synth.SampleRate)
+
+	hasPos := false
+	hasNeg := false
+	for i := 0; i < 100; i++ {
+		s := osc.Advance(harmonics)
+		if s > 0 {
+			hasPos = true
+		}
+		if s < 0 {
+			hasNeg = true
+		}
+	}
+	if !hasPos || !hasNeg {
+		t.Errorf("expected both positive and negative samples; hasPos=%v hasNeg=%v", hasPos, hasNeg)
+	}
+}
+
+func TestOscillatorPhaseWrap(t *testing.T) {
+	harmonics := []synth.HarmonicDef{{Ratio: 1, Amplitude: 1.0}}
+	osc := synth.NewOscillator(440.0, synth.SampleRate)
+
+	for i := 0; i < synth.SampleRate; i++ {
+		osc.Advance(harmonics)
+	}
+	p := osc.Phase()
+	if p < 0 || p >= 1.0 {
+		t.Errorf("expected phase in [0, 1), got %.6f", p)
+	}
+}
+
+func TestOscillatorDistinctFreqs(t *testing.T) {
+	harmonics := []synth.HarmonicDef{{Ratio: 1, Amplitude: 1.0}}
+	osc65 := synth.NewOscillator(65.0, synth.SampleRate)
+	osc440 := synth.NewOscillator(440.0, synth.SampleRate)
+
+	same := true
+	for i := 0; i < 100; i++ {
+		s65 := osc65.Advance(harmonics)
+		s440 := osc440.Advance(harmonics)
+		if s65 != s440 {
+			same = false
+			break
+		}
+	}
+	if same {
+		t.Error("expected oscillators at 65 Hz and 440 Hz to produce different sample sequences")
+	}
+}