test: aggiungi suite di test Flutter

Struttura specchia lib/features/:
- test/features/meal_planner/ — unit (DayPlan, MealPlan, provider) + widget (MealCard)
- test/features/converter/ — unit (ConversionEntry, formule rawToCooked/cookedToRaw)
- test/features/shopping_list/ — unit (ShoppingItem, provider) + widget (ShoppingItemTile)
- test/helpers/pump_app.dart — estensione PumpApp condivisa tra widget test
- integration_test/app_test.dart — e2e navigazione, shopping list, convertitore, meal planner

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

test/features/converter/models/conversion_entry_test.dart

@@ -0,0 +1,65 @@
+import 'package:flutter_test/flutter_test.dart';
+import 'package:biteplan/features/converter/models/conversion_entry.dart';
+
+void main() {
+  group('ConversionEntry', () {
+    test('rawToCooked moltiplica per il fattore di resa', () {
+      const entry = ConversionEntry(
+        food: 'riso basmati',
+        method: 'bollitura',
+        yieldFactor: 3.0,
+      );
+      expect(entry.rawToCooked(100), closeTo(300.0, 0.001));
+      expect(entry.rawToCooked(70), closeTo(210.0, 0.001));
+    });
+
+    test('cookedToRaw divide per il fattore di resa', () {
+      const entry = ConversionEntry(
+        food: 'riso basmati',
+        method: 'bollitura',
+        yieldFactor: 3.0,
+      );
+      expect(entry.cookedToRaw(300), closeTo(100.0, 0.001));
+      expect(entry.cookedToRaw(150), closeTo(50.0, 0.001));
+    });
+
+    test('conversione bidirezionale è consistente', () {
+      const entry = ConversionEntry(
+        food: 'pollo petto',
+        method: 'forno',
+        yieldFactor: 0.67,
+      );
+      final cooked = entry.rawToCooked(140);
+      final backToRaw = entry.cookedToRaw(cooked);
+      expect(backToRaw, closeTo(140, 0.001));
+    });
+
+    test('yield > 1: i cereali aumentano di peso con la cottura', () {
+      const entry = ConversionEntry(
+        food: 'pasta',
+        method: 'bollitura',
+        yieldFactor: 2.1,
+      );
+      expect(entry.rawToCooked(80), greaterThan(80));
+    });
+
+    test('yield < 1: la carne perde peso con la cottura', () {
+      const entry = ConversionEntry(
+        food: 'pollo petto',
+        method: 'forno',
+        yieldFactor: 0.67,
+      );
+      expect(entry.rawToCooked(100), lessThan(100));
+    });
+
+    test('valore limite: 0 grammi restituisce 0', () {
+      const entry = ConversionEntry(
+        food: 'riso',
+        method: 'bollitura',
+        yieldFactor: 3.0,
+      );
+      expect(entry.rawToCooked(0), 0.0);
+      expect(entry.cookedToRaw(0), 0.0);
+    });
+  });
+}