fixes

cmd/cart/product-fetcher_test.go

@@ -0,0 +1,60 @@
+package main
+
+import (
+	"encoding/json"
+	"testing"
+)
+
+func makeProduct(price float64, extra map[string]any) *ProductItem {
+	m := map[string]json.RawMessage{}
+	for k, v := range extra {
+		b, _ := json.Marshal(v)
+		m[k] = b
+	}
+	return &ProductItem{Price: price, Extra: m}
+}
+
+func TestAreaFromItem(t *testing.T) {
+	tests := []struct {
+		name  string
+		extra map[string]any
+		want  float64
+	}{
+		{"floors small window to min", map[string]any{"width": 5, "height": 6}, 0.4}, // 500*600/1e6 = 0.30 -> floor 0.4
+		{"normal window", map[string]any{"width": 10, "height": 10}, 1.0},            // 1000*1000/1e6 = 1.0
+		{"numeric strings", map[string]any{"width": "10", "height": "10"}, 1.0},      // JS Number() parity
+		{"missing height", map[string]any{"width": 10}, 0},
+		{"zero width", map[string]any{"width": 0, "height": 10}, 0},
+		{"non-numeric", map[string]any{"width": "abc", "height": 10}, 0},
+	}
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			got := areaFromItem(makeProduct(0, tc.extra))
+			if got != tc.want {
+				t.Errorf("areaFromItem = %v, want %v", got, tc.want)
+			}
+		})
+	}
+	if got := areaFromItem(nil); got != 0 {
+		t.Errorf("areaFromItem(nil) = %v, want 0", got)
+	}
+}
+
+func TestAccessoryPrice(t *testing.T) {
+	// area 1.0 m^2, child 100.00 -> 100.00 * 100 * 1.0 = 10000 minor units.
+	parent := makeProduct(0, map[string]any{"width": 10, "height": 10})
+	if got := accessoryPrice(parent, makeProduct(100, nil)); got != 10000 {
+		t.Errorf("accessoryPrice = %d, want 10000", got)
+	}
+
+	// area floored to 0.4, child 9952.78 -> round(9952.78 * 100 * 0.4) = 398111.
+	small := makeProduct(0, map[string]any{"width": 5, "height": 6})
+	if got := accessoryPrice(small, makeProduct(9952.78, nil)); got != 398111 {
+		t.Errorf("accessoryPrice = %d, want 398111", got)
+	}
+
+	// parent without dimensions -> area 0 -> price 0.
+	if got := accessoryPrice(makeProduct(0, nil), makeProduct(500, nil)); got != 0 {
+		t.Errorf("accessoryPrice (no dims) = %d, want 0", got)
+	}
+}