Generated test assigns the 'null' value to non-nullable value

[rabinacharya11]

I have a model 'product.dart'. I wanted to test that product using welltested.

here is the model code.

import 'package:json_annotation/json_annotation.dart';
import 'package:welltested/welltested.dart';

part 'product.g.dart';

@JsonSerializable()
@Welltested()
class Product {
  final int id;
  final String title;
  final num price;
  final String description;
  final String image;
  final String category;
  final Rating rating;

  Product(
      {required this.category,
      required this.description,
      required this.id,
      required this.image,
      required this.price,
      required this.title,
      required this.rating});

  factory Product.fromJson(Map<String, dynamic> json) =>
      _$ProductFromJson(json);

  Map<String, dynamic> toJson() => _$ProductToJson(this);
}

@JsonSerializable()
class Rating {
  final num rating;
  final int count;

  Rating({
    required this.count,
    required this.rating,
  });

  factory Rating.fromJson(Map<String, dynamic> json) => _$RatingFromJson(json);
  Map<String, dynamic> toJson() => _$RatingToJson(this);
}

Two test files were generated by welltested ai.

Here is the code for each of the files :

toJson.welltested_test.dart

import 'toJson.welltested_test.mocks.dart';
import 'package:flutter_test/flutter_test.dart';
import 'package:mockito/annotations.dart';
import 'package:mockito/mockito.dart';
import 'package:json_annotation/json_annotation.dart';
import 'package:api_integrations/product.dart';

// Generate mocks for Rating class
@GenerateMocks([Rating])
void main() {
  group('Product toJson method', () {
    test('should return a valid JSON map', () {
      // Arrange
      final ratingMock = MockRating();
      when(ratingMock.rating).thenReturn(4.5);
      when(ratingMock.count).thenReturn(100);
      final product = Product(
        id: 1,
        title: 'Test Product',
        price: 9.99,
        description: 'This is a test product',
        image: 'test_image.jpg',
        category: 'Test Category',
        rating: ratingMock,
      );

      // Act
      final result = product.toJson();

      // Assert
      expect(result, isA<Map<String, dynamic>>());
      expect(result['id'], equals(1));
      expect(result['title'], equals('Test Product'));
      expect(result['price'], equals(9.99));
      expect(result['description'], equals('This is a test product'));
      expect(result['image'], equals('test_image.jpg'));
      expect(result['category'], equals('Test Category'));
      expect(result['rating'], isA<Map<String, dynamic>>());
      expect(result['rating']['rating'], equals(4.5));
      expect(result['rating']['count'], equals(100));
    });

    test('should return a JSON map with null values', () {
      // Arrange
      final product = Product(
        id: 1,
        title: 'Test Product',
        price: null,
        description: null,
        image: null,
        category: null,
        rating: null,
      );

      // Act
      final result = product.toJson();

      // Assert
      expect(result, isA<Map<String, dynamic>>());
      expect(result['id'], equals(1));
      expect(result['title'], equals('Test Product'));
      expect(result['price'], isNull);
      expect(result['description'], isNull);
      expect(result['image'], isNull);
      expect(result['category'], isNull);
      expect(result['rating'], isNull);
    });

    test('should throw an exception if id is null', () {
      // Arrange
      final ratingMock = MockRating();
      when(ratingMock.rating).thenReturn(4.5);
      when(ratingMock.count).thenReturn(100);
      final product = Product(
        id: null,
        title: 'Test Product',
        price: 9.99,
        description: 'This is a test product',
        image: 'test_image.jpg',
        category: 'Test Category',
        rating: ratingMock,
      );

      // Act & Assert
      expect(
          () => product.toJson(), throwsA(isA<JsonUnsupportedObjectError>()));
    });
  });
}

toJson.welltested_test.mocks.dart

// Mocks generated by Mockito 5.4.2 from annotations
// in api_integrations/test/product/0.wt.dart.
// Do not manually edit this file.

// ignore_for_file: no_leading_underscores_for_library_prefixes
import 'package:api_integrations/product.dart' as _i2;
import 'package:mockito/mockito.dart' as _i1;

// ignore_for_file: type=lint
// ignore_for_file: avoid_redundant_argument_values
// ignore_for_file: avoid_setters_without_getters
// ignore_for_file: comment_references
// ignore_for_file: implementation_imports
// ignore_for_file: invalid_use_of_visible_for_testing_member
// ignore_for_file: prefer_const_constructors
// ignore_for_file: unnecessary_parenthesis
// ignore_for_file: camel_case_types
// ignore_for_file: subtype_of_sealed_class

/// A class which mocks [Rating].
///
/// See the documentation for Mockito's code generation for more information.
class MockRating extends _i1.Mock implements _i2.Rating {
  MockRating() {
    _i1.throwOnMissingStub(this);
  }

  @override
  num get rating => (super.noSuchMethod(
        Invocation.getter(#rating),
        returnValue: 0,
      ) as num);
  @override
  int get count => (super.noSuchMethod(
        Invocation.getter(#count),
        returnValue: 0,
      ) as int);
  @override
  Map<String, dynamic> toJson() => (super.noSuchMethod(
        Invocation.method(
          #toJson,
          [],
        ),
        returnValue: <String, dynamic>{},
      ) as Map<String, dynamic>);
}

My pubspec.yaml file

name: api_integrations
description: A new Flutter project.
publish_to: 'none'
version: 0.1.0

environment:
  sdk: '>=3.0.0-408.0.dev <4.0.0'

dependencies:
  flutter:
    sdk: flutter
  http: ^0.13.6
  json_serializable: ^6.6.2
  mockito: ^5.4.2
  welltested: ^1.0.4

dev_dependencies:
  flutter_test:
    sdk: flutter
  flutter_lints: ^2.0.0
  build_runner:

flutter:
  uses-material-design: true

Thank you !