使用 FluentAssertions 比较包含不同类型的两个字典集合

Posted 2023-03-24

【中文标题】使用 FluentAssertions 比较包含不同类型的两个字典集合

【英文标题】：Using FluentAssertions to compare two collections of dictionaries that are containing different types

【发布时间】：2018-09-25 19:08:08

【问题描述】：

从我们的数据库中，我们查询放入ExpandoObject 类型的动态对象集合中的记录集，这些对象在字段上实现IDictionary<string, object>。这些是实际值。

从我们的 SpecFlow BDD 测试中，我们获得了实现 IDictionary<string, string> 的 TableRows 集合。这些是我们的预期值。

使用 FluentAssertions，我们希望使用 actual.Should().BeEquivalentTo(expected) 测试整个集合的等效性。不幸的是，这不起作用，因为当实际值不是 string 类型时，类型不匹配。

我们可以使用actual.Should().BeEquivalentTo(expected, options => options.WithAutoConversion())，但这会使整个实际集合成为IDictionary<string, string> 的集合，这对于比较日期没有用处。

我组装了一个会显示相同问题的测试用例：

var expected = new List<Dictionary<string, string>>();
expected.Add(new Dictionary<string, string>

    "Name", "Moon Inc.",
    "Number", "42",
    "Date", "2018-12-31"
);

var actual = new List<ExpandoObject>();
dynamic eo = new ExpandoObject();
eo.Name = "Moon Inc.";
eo.Number = 42;
eo.Date = new DateTime(2018, 12, 31);

actual.Add(eo);

actual.Should().BeEquivalentTo(expected, options => options);
/* 
    This throws:
    NUnit.Framework.AssertionException: 
    Expected item[0][Number] to be System.String, but found System.Int32.
    Expected item[0][Date] to be System.String, but found System.DateTime.
*/

actual.Should().BeEquivalentTo(expected, options => options.WithAutoConversion());
/*
    This throws:
    NUnit.Framework.AssertionException: 
    Expected item[0][Date] to be "2018-12-31" with a length of 10, 
    but "31-12-2018 0:00:00" has a length of 18.
/*

我尝试在使用方法中使接收类型动态化，例如：

actual.Should().BeEquivalentTo(expected, options => options
    .Using<dynamic>(ctx => ctx.Subject.Should().Be(ctx.Expectation)).WhenTypeIs<DateTime>()
    .Using<dynamic>(ctx => ctx.Subject.Should().Be(ctx.Expectation)).WhenTypeIs<int>());

/* 
    NUnit.Framework.AssertionException: 
    Expected item[0][Number] to be System.String, but found System.Int32.
    Expected item[0][Date] to be System.String, but found System.DateTime.
*/

将双方解析为DateTime 并使用自动转换也不起作用，因为actual 类型不被视为DateTime，而是string：

actual.Should().BeEquivalentTo(expected, options => options
    .Using<dynamic>(
        ctx =>
            DateTime.ParseExact(ctx.Subject, "yyy-MM-dd", CultureInfo.InvariantCulture)
            .Should().Be(DateTime.ParseExact(ctx.Expectation, "yyy-MM-dd", CultureInfo.InvariantCulture)))
    .WhenTypeIs<DateTime>()
    .WithAutoConversion());

/*
    NUnit.Framework.AssertionException: 
    Expected item[0][Date] to be "2018-12-31" with a length of 10, 
    but "31-12-2018 0:00:00" has a length of 18.
*/

FluentAssertions 有什么方法可以实现这一点吗？

【参考方案1】：

如果没有其他帮助，您可以像这样实现自定义IEquivalencyStep：

class WeakDateEquivalencyStep : IEquivalencyStep 
    public bool CanHandle(IEquivalencyValidationContext context, IEquivalencyAssertionOptions config) 
        if (context.IsRoot)
            return false;
        // handles situations when subject is date
        // but expectation is string
        return context.Subject is DateTime && context.Expectation is string;
    

    public bool Handle(IEquivalencyValidationContext context, IEquivalencyValidator parent, IEquivalencyAssertionOptions config) 
        DateTime exp;
        // we know that expection is string here
        if (!DateTime.TryParse((string) context.Expectation, CultureInfo.InvariantCulture, DateTimeStyles.None, out exp)) 
            // do something, your spec is invalid
            throw new Exception($"Value context.Expectation does not represent valid date time");
        

        context.Subject.Should().Be(exp, context.Because, context.BecauseArgs);
        return true;
    

然后

actual.Should().BeEquivalentTo(expected, options => 
   options.Using(new WeakDateEquivalencyStep()).WithAutoConversion());

【讨论】：

这非常适合我的情况，有了这些知识，我也可以将它扩展到其他类型。非常感谢！