step one

internal/numerics/search_test.go

@@ -0,0 +1,28 @@
+package numerics
+
+import "testing"
+
+func TestBisect(t *testing.T) {
+	// f(i) = 10*i, monotone increasing.
+	f := func(i int) float64 { return 10 * float64(i) }
+
+	// target = 25 → largest i with 10i < 25 is i=2
+	if got := Bisect(0, 10, 25, f); got != 2 {
+		t.Errorf("Bisect target=25 = %d, want 2", got)
+	}
+
+	// target on boundary: target = 30, condition is target <= f(mid) so f(3)=30 → not less; want 2
+	if got := Bisect(0, 10, 30, f); got != 2 {
+		t.Errorf("Bisect target=30 = %d, want 2", got)
+	}
+
+	// target below all values
+	if got := Bisect(0, 10, -5, f); got != 0 {
+		t.Errorf("Bisect target=-5 = %d, want 0", got)
+	}
+
+	// target above all values
+	if got := Bisect(0, 10, 1000, f); got != 10 {
+		t.Errorf("Bisect target=1000 = %d, want 10", got)
+	}
+}