test(shopinbit): add persistence tests for car research resume flow

diff --git a/test/shopinbit/car_research_persistence_test.dart b/test/shopinbit/car_research_persistence_test.dart
new file mode 100644
index 0000000..10df9ae
--- /dev/null
+++ b/test/shopinbit/car_research_persistence_test.dart
@@ -0,0 +1,114 @@
+import 'dart:convert';
+
+import 'package:flutter_test/flutter_test.dart';
+import 'package:stackwallet/models/shopinbit/shopinbit_order_model.dart';
+
+// Parses "Key: Value\n" car research description; strips " EUR" from Budget.
+Map<String, String> _parseCarRequestDescription(String desc) {
+  final result = <String, String>{};
+  for (final line in desc.split('\n')) {
+    final separatorIndex = line.indexOf(': ');
+    if (separatorIndex == -1) continue;
+    final key = line.substring(0, separatorIndex);
+    var value = line.substring(separatorIndex + 2);
+    if (key == 'Budget') {
+      value = value.replaceAll(' EUR', '');
+    }
+    result[key] = value;
+  }
+  return result;
+}
+
+void main() {
+  group('car research persistence', () {
+    group('requestDescription parsing', () {
+      test('parses all six fields from canonical format', () {
+        const desc =
+            'Brand: Toyota\n'
+            'Model: Corolla\n'
+            'Condition: used\n'
+            'Description: sedan\n'
+            'Budget: 10000 EUR\n'
+            'Delivery country: DE';
+        final parsed = _parseCarRequestDescription(desc);
+        expect(parsed['Brand'], 'Toyota');
+        expect(parsed['Model'], 'Corolla');
+        expect(parsed['Condition'], 'used');
+        expect(parsed['Description'], 'sedan');
+        expect(parsed['Budget'], '10000');
+        expect(parsed['Delivery country'], 'DE');
+      });
+    });
+
+    group('carResearchPaymentLinks JSON round-trip', () {
+      test('encode then decode preserves all keys and values', () {
+        final original = {
+          'BTC': 'bitcoin:abc?amount=0.1',
+          'ETH': 'ethereum:def',
+        };
+        final encoded = jsonEncode(original);
+        final decoded = (jsonDecode(encoded) as Map<String, dynamic>).map(
+          (k, v) => MapEntry(k, v as String),
+        );
+        expect(decoded, equals(original));
+      });
+    });
+
+    group('isPendingPayment defaults false', () {
+      test('new ShopInBitOrderModel has isPendingPayment == false', () {
+        final model = ShopInBitOrderModel();
+        expect(model.isPendingPayment, isFalse);
+      });
+    });
+
+    group(
+      'toIsarTicket/fromIsarTicket round-trip for pending payment fields',
+      () {
+        test('isPendingPayment round-trips', () {
+          final model = ShopInBitOrderModel()
+            ..isPendingPayment = true
+            ..carResearchExpiresAt = DateTime(2026, 6, 1)
+            ..carResearchPaymentLinks = '{"BTC":"link"}';
+          final ticket = model.toIsarTicket();
+          final restored = ShopInBitOrderModel.fromIsarTicket(ticket);
+          expect(restored.isPendingPayment, isTrue);
+          expect(restored.carResearchExpiresAt, DateTime(2026, 6, 1));
+          expect(restored.carResearchPaymentLinks, '{"BTC":"link"}');
+        });
+      },
+    );
+
+    group('live invoice routes to payment view', () {
+      test('expiresAt in the future means invoice is live', () {
+        final expiresAt = DateTime.now().add(const Duration(hours: 1));
+        expect(expiresAt.isAfter(DateTime.now()), isTrue);
+      });
+    });
+
+    group('expired invoice routes to fee view', () {
+      test('expiresAt in the past means invoice is expired', () {
+        final expiresAt = DateTime.now().subtract(const Duration(hours: 1));
+        expect(expiresAt.isAfter(DateTime.now()), isFalse);
+      });
+    });
+
+    group('clearing isPendingPayment preserves other fields', () {
+      test(
+        'all other model fields unchanged after clearing isPendingPayment',
+        () {
+          final model = ShopInBitOrderModel()
+            ..displayName = 'Test User'
+            ..requestDescription =
+                'Brand: BMW\nModel: X5\nCondition: new\nDescription: suv\nBudget: 50000 EUR\nDelivery country: AT'
+            ..carResearchInvoiceId = 'inv-123'
+            ..isPendingPayment = true;
+          model.isPendingPayment = false;
+          expect(model.isPendingPayment, isFalse);
+          expect(model.displayName, 'Test User');
+          expect(model.carResearchInvoiceId, 'inv-123');
+          expect(model.requestDescription, startsWith('Brand: BMW'));
+        },
+      );
+    });
+  });
+}