Implemented and fixed many issues

Common/Client/go/wshub/zoom_test.go

@@ -1,6 +1,65 @@
 package wshub
 
-import "testing"
+import (
+	"math"
+	"testing"
+)
+
+// A scope's envelope must not lose a spike, however narrow, and must stay in
+// time order so it can be plotted as a single trace.
+func TestMinMaxDecimateKeepsExtremes(t *testing.T) {
+	const n = 10000
+	ts := make([]float64, n)
+	vs := make([]float64, n)
+	for i := range ts {
+		ts[i] = float64(i) * 1e-6
+		vs[i] = math.Sin(float64(i) * 0.01)
+	}
+	// A one-sample spike in each direction: exactly what plain decimation drops.
+	vs[4321] = 12.5
+	vs[6789] = -9.75
+
+	dt, dv := minMaxDecimate(ts, vs, 200)
+	if len(dt) > 200 || len(dt) != len(dv) {
+		t.Fatalf("got %d t / %d v points, want <= 200 of each", len(dt), len(dv))
+	}
+	hiSeen, loSeen := false, false
+	for i := range dv {
+		switch dv[i] {
+		case 12.5:
+			hiSeen = true
+			if dt[i] != ts[4321] {
+				t.Errorf("spike kept at t=%v, want %v: timestamps must be the real ones", dt[i], ts[4321])
+			}
+		case -9.75:
+			loSeen = true
+		}
+		if i > 0 && dt[i] < dt[i-1] {
+			t.Fatalf("output is not time-ordered at %d: %v after %v", i, dt[i], dt[i-1])
+		}
+	}
+	if !hiSeen || !loSeen {
+		t.Errorf("envelope lost a spike (max kept=%v, min kept=%v)", hiSeen, loSeen)
+	}
+}
+
+func TestMinMaxDecimatePassesShortInputThrough(t *testing.T) {
+	ts := []float64{1, 2, 3}
+	vs := []float64{4, 5, 6}
+	dt, dv := minMaxDecimate(ts, vs, 200)
+	if len(dt) != 3 || dv[2] != 6 {
+		t.Errorf("input below the budget was altered: %v / %v", dt, dv)
+	}
+	// A flat bucket contributes one point, not two: nothing is invented.
+	flatT := make([]float64, 100)
+	flatV := make([]float64, 100)
+	for i := range flatT {
+		flatT[i] = float64(i)
+	}
+	if ft, _ := minMaxDecimate(flatT, flatV, 10); len(ft) != 5 {
+		t.Errorf("flat input decimated to %d points, want 5 (one per bucket)", len(ft))
+	}
+}
 
 func TestZoomPoints(t *testing.T) {
 	cases := []struct {