Can Fluent Assertions use a string-insensitive comparison for IEnumerable?

Question

I've got a pair of Lists I'm trying to compare using Fluent Assertions. I can code up a comparison easily, but I'd like to use Fluent Assertions so that I can get the reason to show up in the test failed message.

Everything I've seen so far seems to using the default Object.Equals comparison, which is case-sensitive. I can't seem to pass an IComparer to the Equal or Contains methods, so is there any other way?

[TestMethod()]
public void foo()
{
  var actual = new List<string> { "ONE", "TWO", "THREE", "FOUR" };
  var expected = new List<string> { "One", "Two", "Three", "Four" };

  actual.Should().Equal(expected);
}

score 31 · Answer 1 · edited Sep 15 '21 at 06:39

31

In later versions of Fluent Assertions, one can use following:

stringValue.Should().BeEquivalentTo(stringToCompare);

Metadata Summary

Asserts that a string is exactly the same as another string, including any leading or trailing whitespace, with the exception of the casing.

FluentAssertions 2.2.0.0

Which works in the version that I use.

edited Sep 15 '21 at 06:39

Bennett Yeo

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answered Apr 07 '14 at 08:58

TarasB

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Now I have the opposite question: I need it to see casing differences. Am I stuck with my own handwritten comparison and then checking result being true/false? – ecth Aug 01 '22 at 09:30

score 3 · Accepted Answer · answered Mar 27 '12 at 06:15

3

We could add an optional lambda expression to the Equal() method. Then, you could do something like

[TestMethod()] 
public void foo() 
{ 
   var actual = new List<string> { "ONE", "TWO", "THREE", "FOUR" }; 
   var expected = new List<string> { "One", "Two", "Three", "Four" }; 

  actual.Should().Equal(expected, 
    (o1, o2) => string.Compare(o1, o2, StringComparison.InvariantCultureIgnoreCase))
}

A IComparer would also be possible, but I think the occasional exception to Equal()'s default behavior wouldn't warrant an additional custom-written class. In fact, a separate IComparer might ever obscure the intention of the test. Let me know what you guys think is the best solution, so I can add it as an issue on Codeplex for release 1.8.0.

answered Mar 27 '12 at 06:15

Dennis Doomen

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That's pretty much exactly what I wanted. I'll use one of the workarounds below for now, and I'll keep an eye on that next version. – Zugbo Mar 27 '12 at 15:19
The proposed solution is now implemented in the trunk and will be part of the upcoming release 2.0.0. – Dennis Doomen Apr 22 '12 at 19:44
It's now in the public beta http://fluentassertions.codeplex.com/releases/view/82423 – Dennis Doomen Aug 25 '12 at 14:34

score 1 · Answer 3 · edited May 30 '12 at 09:14

1

How about adding a new Fluent assertion via an extention method (or two)? I've written code to add a .EqualInsensitively(...) to the available fluent assertions for a collection of strings.

I've put the code to implement this on an external pastebin because its a little long and the MS-PL might not be compatible with CC-Wiki.

Use something like this:

private static void Main()
{
    var mylist = new List<string> {"abc", "DEF", "GHI"};
    mylist.Should().EqualInsensitively(new[] {"AbC", "def", "GHI"})
      .And.NotContain(string.Empty); //Emaple of chaining
}

edited May 30 '12 at 09:14

dplante

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answered Mar 26 '12 at 20:12

Kevin Cathcart

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4

the pastebin link 404s – Damian Green Jul 07 '16 at 18:13

score 0 · Answer 4 · answered Mar 26 '12 at 18:42

0

you could wirte a extension method for IEnumerable<string> yourself (this is how I do this stuff) and I thing some Unit-Testframeworks already do so (FSUnit AFAIK)

Here is a simple example (you could improve a lot - but it should do)

public static AssertEqualSetCaseInsensitive(this IEnumerable<string> actual, IEnumerable<string> expected)
{
   if (actual.Count() != expected.Count())
      Assert.Fail("not same number of elements");

   if (!actual.All(a => expected.Any(e => e.ToLower() == a.ToLower()))
      Assert.Fail("not same sets");
}

just use like

actual.AssertEqualSetCaseInsensitive(expected);

answered Mar 26 '12 at 18:42

Random Dev

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"I can code up a comparison easily, but I'd like to use Fluent Assertions" – bzlm Mar 26 '12 at 18:50
If I do have to write code, this is probably the way I'd do it, but ideally someone is going to show me some method I hadn't seen yet in the library. – Zugbo Mar 26 '12 at 18:56

Can Fluent Assertions use a string-insensitive comparison for IEnumerable?

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