dart - 如何在 Dart 单元测试中通过其状态(所有属性值)断言对象？

Question

我有一个类(当然比例子有更多的属性)。

如何编写下面的简单测试？我知道 Dart 中的平等是由对象实例决定的。如何比较完整的对象状态？我也用 same 匹配器进行了测试，但没有成功。

import 'package:test/test.dart';

class UnderTesting {
  var a;
  var b;
  UnderTesting({this.a, this.b});
}

void main() {
  test("compare objects", () {
    final obj1 = UnderTesting(a:1, b:2);
    final obj2 = UnderTesting(a:1, b:2);
    
    // Next will fail because it is checking if it is the same instance
    expect(obj1, equals(obj2));
  } );
}

Answer 1

您需要为 UnderTesting 覆盖 == 运算符(因此也应该覆盖 hashCode)。 equals 的文档告诉我们如何进行相等性测试:

If [expected] is a [Matcher], then it matches using that. Otherwise it tests for equality using == on the expected value.

所以你的代码应该是这样的:

import 'package:test/test.dart';
import 'package:quiver/core.dart';

class UnderTesting {
  int a;
  int b;
  UnderTesting({this.a, this.b});

  @override
  bool operator ==(Object other) =>
      (other is UnderTesting) ? (a == other.a && b == other.b) : false;

  @override
  int get hashCode => hash2(a, b);
}

void main() {
  test("compare objects", () {
    final obj1 = UnderTesting(a: 1, b: 2);
    final obj2 = UnderTesting(a: 1, b: 2);

    expect(obj1, equals(obj2)); // All tests passed!
  });
}

我可以推荐 quiver 包来制作简单的 hashCode 实现:https://pub.dev/documentation/quiver/latest/quiver.core/quiver.core-library.html