Gamma-W1-T7: gate PSOLA's two untested wires, fix the cadence test's contradictory rationale, add a vacuity guard

tests/test_pitch_shift.cpp

@@ -780,10 +780,11 @@ static void testStretchCadenceCornerArtifactEnergyAtRate2ShiftQuarter() {
     const std::size_t outFrames = 60000;
     const std::size_t from = 20000, len = 32768;
 
-    // Below the safe floor (P > 315 frames): the cadence inequality predicts real damage,
-    // measured at 7-21% (see above). The threshold (5%) sits above the alignable control's
-    // near-zero floor and under the observed range, so it discriminates a genuine cadence hit
-    // from a clean render; the ceiling (30%) is a generous margin above the highest measured
+    // Below the safe floor (P > 315 frames): per the header's CORRECTED note, this raw reading
+    // is mostly the metric's own mainlobe-leakage floor, not cadence damage (the real excess is
+    // ~0.2-0.5%, asserted in testCadenceCornerIsUnmovedByAPitchSynchronousSplice). The bounds
+    // below are a RAW-READING STABILITY TRIPWIRE, not a discriminator — they catch a large swing
+    // in the raw measurement; the ceiling (30%) is a generous margin above the highest measured
     // value, there to catch a much worse regression rather than to chase today's exact number.
     for (double period : {500.0, 600.0, 700.0}) {
         const double f0 = 1.0 / period;
@@ -918,7 +919,7 @@ static void testThirtyHertzSplicesAlignOnceTheSourcePeriodIsKnown() {
         {"34 Hz +2 st, rate 1.0", 34.0, 1.0, 2.0},   // control: alignable without a period
         {"34 Hz rate 2.0",        34.0, 2.0, 0.0},
     };
-    double controlWorst = 0.0, subjectWorst = 0.0;
+    double controlWorst = 0.0, subjectWorst = 0.0, subjectOffWorst = 0.0;
     for (const Row& r : rows) {
         const double period = 44100.0 / r.freq;
         std::vector<AudioSample> src(srcLen);
@@ -938,8 +939,12 @@ static void testThirtyHertzSplicesAlignOnceTheSourcePeriodIsKnown() {
         std::printf("  [30 Hz] %-24s (want %6.1f fr, metric floor %.2f%%) excess energy: "
                     "fixed window %6.2f%% -> pitch-synchronous %6.2f%%\n", r.label, want, floor,
                     pctOff, pctOn);
-        if (r.freq == 34.0) controlWorst = std::max(controlWorst, pctOn);
-        else subjectWorst = std::max(subjectWorst, pctOn);
+        if (r.freq == 34.0) {
+            controlWorst = std::max(controlWorst, pctOn);
+        } else {
+            subjectWorst = std::max(subjectWorst, pctOn);
+            subjectOffWorst = std::max(subjectOffWorst, pctOff);
+        }
     }
     // 30 Hz stops being a special case: with the period known its excess over the metric's own
     // floor is no worse than the alignable neighbour's, measured identically. Against the
@@ -949,6 +954,11 @@ static void testThirtyHertzSplicesAlignOnceTheSourcePeriodIsKnown() {
                 subjectWorst, controlWorst);
     CHECK(subjectWorst < 0.10);
     CHECK(subjectWorst <= controlWorst + 0.05);  // 0.05 absorbs the floor subtraction's sign noise
+    // Vacuity guard, matching testTwentyNineHertzAtRateTwoKeepsItsPitch's sibling check: the
+    // FIXED-WINDOW (no period set) arm is asserted too, so a setSourcePeriod that silently did
+    // nothing would render both arms identically and fail here rather than passing on the
+    // absolute bound above by luck.
+    CHECK(subjectOffWorst > subjectWorst + 1.0);
 }
 
 // The sharpest single symptom of the geometry: at 29 Hz the nearest multiple misses the