feat(tests): updated tests coverage to 66.5%

test/features/registration/models/user_registration_model_test.dart

@@ -123,5 +123,50 @@ void main() {
       expect(model.hasHypo, 1);
       expect(model.hasHyper, 0);
     });
+
+    test('toJson serializes UserRegistrationSheet correctly', () {
+      const model = UserRegistrationSheet(
+        firstName: 'John',
+        lastName: 'Doe',
+        email: 'john.doe@example.com',
+        password: 'password123',
+        passwordConfirmation: 'password123',
+        termsAccepted: 'accepted',
+        birthdate: '1990-01-01',
+        gender: 'male',
+        location: 'New York',
+        responseBody: '{}',
+        lang: 'en',
+        weight: 75,
+        height: 180,
+        phone: '+1234567890',
+        chestCircumference: 100,
+        waistCircumference: 80,
+        hipCircumference: 90,
+        bloodPressureUp: 120,
+        bloodPressureDown: 80,
+        hasHypo: 0,
+        hasHyper: 0,
+        aboutAllergy: 'None',
+        aboutTakingPils: 'None',
+        aboutSportHobbies: 'Running',
+        favoriteFoods: 'Pizza',
+        unfavoriteFoods: 'Broccoli',
+        additionalInfo: 'No additional info',
+        activityCoefficient: 1.5,
+      );
+
+      final json = model.toJson();
+
+      expect(json['first_name'], 'John');
+      expect(json['last_name'], 'Doe');
+      expect(json['email'], 'john.doe@example.com');
+      expect(json['password'], 'password123');
+      expect(json['password_confirmation'], 'password123');
+      expect(json['terms'], 'accepted');
+      expect(json['weight'], 75);
+      expect(json['height'], 180);
+      expect(json['activity_coefficient'], 1.5);
+    });
   });
 }