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

test/models/group_test.dart

@@ -0,0 +1,100 @@
+import 'package:flutter_test/flutter_test.dart';
+import 'package:travel_mate/models/group.dart';
+
+void main() {
+  group('Group Model Tests', () {
+    const id = 'group1';
+    const name = 'Paris Trip Group';
+    const tripId = 'trip1';
+    const createdBy = 'user1';
+    final createdAt = DateTime(2023, 1, 1);
+    final updatedAt = DateTime(2023, 1, 2);
+    const memberIds = ['user1', 'user2'];
+
+    final groupInstance = Group(
+      id: id,
+      name: name,
+      tripId: tripId,
+      createdBy: createdBy,
+      createdAt: createdAt,
+      updatedAt: updatedAt,
+      memberIds: memberIds,
+    );
+
+    test('props correct', () {
+      expect(groupInstance.id, id);
+      expect(groupInstance.name, name);
+      expect(groupInstance.tripId, tripId);
+      expect(groupInstance.createdBy, createdBy);
+      expect(groupInstance.createdAt, createdAt);
+      expect(groupInstance.updatedAt, updatedAt);
+      expect(groupInstance.memberIds, memberIds);
+      expect(groupInstance.members, isEmpty);
+    });
+
+    group('fromMap', () {
+      test('returns correct group from valid map', () {
+        final map = {
+          'name': name,
+          'tripId': tripId,
+          'createdBy': createdBy,
+          'createdAt': createdAt.millisecondsSinceEpoch,
+          'updatedAt': updatedAt.millisecondsSinceEpoch,
+          'memberIds': memberIds,
+        };
+        final fromMapGroup = Group.fromMap(map, id);
+
+        expect(fromMapGroup.id, id);
+        expect(fromMapGroup.name, name);
+        expect(fromMapGroup.tripId, tripId);
+        expect(fromMapGroup.createdBy, createdBy);
+        expect(fromMapGroup.createdAt, createdAt);
+        expect(fromMapGroup.updatedAt, updatedAt);
+        expect(fromMapGroup.memberIds, memberIds);
+      });
+
+      test('handles missing values gracefully', () {
+        final map = <String, dynamic>{};
+        final fromMapGroup = Group.fromMap(map, id);
+
+        expect(fromMapGroup.id, id);
+        expect(fromMapGroup.name, '');
+        expect(fromMapGroup.tripId, '');
+        expect(fromMapGroup.createdBy, '');
+        expect(fromMapGroup.memberIds, isEmpty);
+      });
+    });
+
+    group('toMap', () {
+      test('returns correct map', () {
+        final map = groupInstance.toMap();
+
+        expect(map['name'], name);
+        expect(map['tripId'], tripId);
+        expect(map['createdBy'], createdBy);
+        expect(map['createdAt'], createdAt.millisecondsSinceEpoch);
+        expect(map['updatedAt'], updatedAt.millisecondsSinceEpoch);
+        expect(map['memberIds'], memberIds);
+      });
+    });
+
+    group('copyWith', () {
+      test('returns object with updated values', () {
+        const newName = 'London Trip Group';
+        final updatedGroup = groupInstance.copyWith(name: newName);
+
+        expect(updatedGroup.name, newName);
+        expect(updatedGroup.id, id);
+        expect(updatedGroup.tripId, tripId);
+      });
+
+      test('returns distinct object but same values if no args', () {
+        final copy = groupInstance.copyWith();
+        expect(copy.id, groupInstance.id);
+        expect(copy.name, groupInstance.name);
+        // Note: Group does not implement == so we check reference inequality but value equality manually or trust fields are copied
+        expect(identical(copy, groupInstance), isFalse);
+      });
+    });
+  });
+}