FluentAssertions - 如何使ShouldBeEquivalentTo将empty和null比较为相等

Question

我正在使用Fluent Assertion库作为我的单元测试中的一些自定义序列化代码的一部分,我正在寻找一种方法来强制将ShouldBeEquivalentTo比较为null和空列表.

基本上,我的测试看起来像:

    [Test]
    public void Should_be_xxx()
    {
        ClassWithList one = new ClassWithList { Id = "ten", Items = null };

        string serialized = Serialize(one);
        ClassWithList two = Deserialize(serialized);

        two.ShouldBeEquivalentTo(one);
    }

但是,Deserialize方法的一个特性是,如果输入数据中缺少集合类型,它会将反序列化类的属性设置为空列表,而不是null.所以,非常简化,我最终得到的情况是实例二,Items = new List<string>而不是null.

显然,我可以one.Items = new List<string>()在比较之前设置,但实际上我有大量复杂的域对象,我在这些方法中断言,我正在寻找一个通用的解决方案.换句话说,有没有人知道如何进行以下测试:

    public class ClassWithList
    {
        public string Id { get; set; }
        public List<string> Items { get; set; }
    }

    [Test]
    public void Should_be_xxx()
    {
        ClassWithList one = new ClassWithList { Id = "ten", Items = null };
        ClassWithList two = new ClassWithList { Id = "ten", Items = new List<string>() };

        two.ShouldBeEquivalentTo(one);
    }

换句话说,我希望将以下测试应用于类X中的所有集合,作为比较等效性的一部分:

  if (subject.Items == null)
  {
     expected.Items.Should().BeEmpty();
  }
  else
  {
     expected.Items.Should().BeEquivalentTo(subject.Items);
  }

Answer 1

您必须实现自定义的 'IEquivalencyStep' 或 u.se 'options.Using(custom action).WhenTypeIs(predicate)。

Answer 2

根据上面来自丹尼斯的信息，我能够通过以下实际代码解决这个问题：

    public class ClassWithList
    {
        public string Id { get; set; }
        public List<string> Items { get; set; }
        public List<ClassWithList> Nested { get; set; }
    }

    [TestClass]
    public class Test
    {
        [TestMethod]
        public void Should_compare_null_to_empty()
        {
            ClassWithList one = new ClassWithList { Id = "ten", Items = null, Nested = new List<ClassWithList> { new ClassWithList { Id = "a" } } };
            ClassWithList two = new ClassWithList { Id = "ten", Items = new List<string>(), Nested = new List<ClassWithList> { new ClassWithList { Id = "a", Items = new List<string>(), Nested = new List<ClassWithList> { } } } };

            two.ShouldBeEquivalentTo(one, opt => opt
                .Using<IEnumerable>(CheckList)
                .When(info => typeof(IEnumerable).IsAssignableFrom(info.CompileTimeType)));
        }

        private void CheckList(IAssertionContext<IEnumerable> a)
        {
            if (a.Expectation == null)
            {
                a.Subject.Should().BeEmpty();
            }
            else
            {
                a.Subject.ShouldBeEquivalentTo(a.Expectation, opt => opt
                    .Using<IEnumerable>(CheckList)
                    .When(info => typeof(IEnumerable).IsAssignableFrom(info.CompileTimeType)));
            }
        }
    }