Flutter单元测试中Right<Failure, List>相等性校验失败求助

测试代码：

expect(result, equals(Right<Failure, List>(userTestEntityList)));

测试失败异常：

TestFailure (Expected: Right<Failure, List>:<Right([UserEntity(1, lolo, Laurent, Marin), UserEntity(2, roro, Robert, Redford)])> Actual: Right<Failure, List>:<Right([UserEntity(1, lolo, Laurent, Marin), UserEntity(2, roro, Robert, Redford)])> )

我已经尝试过两种方式定义UserEntity类，但问题仍未解决：

1. 使用Equatable实现 #

import 'package:equatable/equatable.dart';

class UserEntity extends Equatable {
  const UserEntity({
    this.id,
    this.pseudo,
    this.firstName,
    this.lastName,
  });

  /// A description for id
  final int? id;

  /// A description for pseudo
  final String? pseudo;

  /// A description for firstName
  final String? firstName;

  /// A description for lastName
  final String? lastName;

  @override
  List<Object?> get props => [
        id,
        pseudo,
        firstName,
        lastName,
      ];
    
}

2. 重写operator==和hashCode #

class UserEntity {
  const UserEntity({
    this.id,
    this.pseudo,
    this.firstName,
    this.lastName,
  });

  /// A description for id
  final int? id;

  /// A description for pseudo
  final String? pseudo;

  /// A description for firstName
  final String? firstName;

  /// A description for lastName
  final String? lastName;


  @override
  bool operator ==(Object other) =>
      identical(this, other) ||
      other is UserEntity &&
          runtimeType == other.runtimeType &&
          id == other.id &&
          pseudo == other.pseudo &&
          firstName == other.firstName &&
          lastName == other.lastName;

  @override
  int get hashCode =>
      id.hashCode ^ pseudo.hashCode ^ firstName.hashCode ^ lastName.hashCode;

}

问题原因与解决方案 #

问题出在List的相等性检查上：Dart中普通List的==默认是引用相等，即使两个List的元素完全一致，只要是不同的实例，就会判定为不相等。而当前测试直接比较整个Right对象，其内部的List会用默认的引用相等规则判定，导致测试失败。

你可以通过以下两种方式解决：

方式一：拆分检查，单独验证List元素

先确认result是Right类型，再用orderedEquals（要求元素顺序一致）或unorderedEquals（不要求顺序）验证内部List的元素：

// 先验证类型
expect(result, isA<Right<Failure, List<UserEntity>>>());
// 再验证List元素相等
expect((result as Right<Failure, List<UserEntity>>).value, orderedEquals(userTestEntityList));

方式二：使用自定义的可比较List（比如EquatableList）

如果你希望List本身能通过元素相等来判定相等，可以使用equatable包提供的EquatableList，这样在比较Right对象时，内部的List会按元素相等规则判定：

// 使用EquatableList创建测试列表
final userTestEntityList = EquatableList.of([
  UserEntity(id: 1, pseudo: 'lolo', firstName: 'Laurent', lastName: 'Marin'),
  UserEntity(id: 2, pseudo: 'roro', firstName: 'Robert', lastName: 'Redford'),
]);

// 测试代码保持不变，泛型指定为EquatableList<UserEntity>
expect(result, equals(Right<Failure, EquatableList<UserEntity>>(userTestEntityList)));

另外，建议明确指定泛型类型为List<UserEntity>而非List，这样类型检查更严格，也能避免潜在的类型相关问题。

内容的提问来源于stack exchange，提问作者Laurent