feat: Introduce comprehensive unit tests for models and BLoCs using mockito and bloc_test, and refine TripBloc error handling.

test/models/trip_test.dart

@@ -0,0 +1,128 @@
+import 'package:cloud_firestore/cloud_firestore.dart';
+import 'package:flutter_test/flutter_test.dart';
+import 'package:travel_mate/models/trip.dart';
+
+void main() {
+  group('Trip Model Tests', () {
+    const id = 'trip1';
+    const title = 'Summer Vacation';
+    const description = 'Trip to the beach';
+    const location = 'Miami';
+    final startDate = DateTime(2023, 6, 1);
+    final endDate = DateTime(2023, 6, 10);
+    const createdBy = 'user1';
+    final createdAt = DateTime(2023, 1, 1);
+    final updatedAt = DateTime(2023, 1, 2);
+    const budget = 2000.0;
+    const participants = ['user1', 'user2', 'user3'];
+
+    final trip = Trip(
+      id: id,
+      title: title,
+      description: description,
+      location: location,
+      startDate: startDate,
+      endDate: endDate,
+      createdBy: createdBy,
+      createdAt: createdAt,
+      updatedAt: updatedAt,
+      budget: budget,
+      participants: participants,
+      status: 'active',
+    );
+
+    test('supports value equality', () {
+      final trip2 = Trip(
+        id: id,
+        title: title,
+        description: description,
+        location: location,
+        startDate: startDate,
+        endDate: endDate,
+        createdBy: createdBy,
+        createdAt: createdAt,
+        updatedAt: updatedAt,
+        budget: budget,
+        participants: participants,
+        status: 'active',
+      );
+      expect(trip, equals(trip2));
+    });
+
+    group('Helpers', () {
+      test('durationInDays returns correct number of days', () {
+        // 1st to 10th inclusive = 10 days
+        expect(trip.durationInDays, 10);
+      });
+
+      test('totalParticipants includes creator + participants list count?', () {
+        // Source code says: participants.length + 1
+        // participants has 3 items. So total should be 4.
+        expect(trip.totalParticipants, 4);
+      });
+
+      test('budgetPerParticipant calculation', () {
+        // 2000 / 4 = 500
+        expect(trip.budgetPerParticipant, 500.0);
+      });
+
+      test(
+        'status checks logic (mocking DateTime.now is tricky without injection, skipping exact time logic or testing logic assumption only)',
+        () {
+          // For simple unit tests without time mocking, we can create trips with dates relative to "now".
+          final now = DateTime.now();
+
+          final pastTrip = trip.copyWith(
+            startDate: now.subtract(const Duration(days: 10)),
+            endDate: now.subtract(const Duration(days: 5)),
+            status: 'completed',
+          );
+          expect(pastTrip.isCompleted, isTrue);
+
+          final futureTrip = trip.copyWith(
+            startDate: now.add(const Duration(days: 5)),
+            endDate: now.add(const Duration(days: 10)),
+            status: 'active',
+          );
+          expect(futureTrip.isUpcoming, isTrue);
+
+          final activeTrip = trip.copyWith(
+            startDate: now.subtract(const Duration(days: 2)),
+            endDate: now.add(const Duration(days: 2)),
+            status: 'active',
+          );
+          expect(activeTrip.isActive, isTrue);
+        },
+      );
+    });
+
+    group('fromMap', () {
+      test('parses standard Map inputs correctly', () {
+        final map = {
+          'title': title,
+          'description': description,
+          'location': location,
+          'startDate': startDate
+              .toIso8601String(), // _parseDateTime handles String
+          'endDate': Timestamp.fromDate(
+            endDate,
+          ), // _parseDateTime handles Timestamp
+          'createdBy': createdBy,
+          'createdAt':
+              createdAt.millisecondsSinceEpoch, // _parseDateTime handles int
+          'updatedAt': updatedAt, // _parseDateTime handles DateTime
+          'budget': budget,
+          'participants': participants,
+          'status': 'active',
+        };
+        final fromMapTrip = Trip.fromMap(map, id);
+
+        expect(fromMapTrip.id, id);
+        expect(fromMapTrip.title, title);
+        // Dates might vary slightly due to precision if using milliseconds vs microseconds, checking explicitly later
+        expect(fromMapTrip.description, description);
+        expect(fromMapTrip.budget, budget);
+      });
+    });
+  });
+}