The testing method WithCustomState doesn't work properly when the state is a string resulting from a concatenation.

How to reproduce: Add a validation that has a custom state as follow: .WithState(x => "Test" + "123");

Add a unit test for this validation and try to assert it as follow: .WithCustomState("Test123");

The test will fail with the message:

Message: 
        FluentValidation.TestHelper.ValidationTestException : Expected custom state of 'Test123'. Actual state was 'Test123'

I have got the same error using no matter what form of concatenation: StrigBuilder, String.Format, $ operator, + operator.

If you remove the concatenation from the validator and use it just as follow, the test works fine: .WithState(x => "Test123");

The nuget version I used is the latest at this moment: 9.5.1.

Could someone check that please? Thanks.

[JeremySkinner]

I see what’s happening. Internally a reference equality check is being performed. This example illustrates the problem:

object s1 = "Test" + 123.ToString();
object s2 = "Test123";

bool check1 = s1 == s2; // False
bool check2 = s2.Equals(s1); // True

Becuase the == operator is used against variables of type object, the wrong type equality check is performed. Internally this is what FluentValidation is doing.

When explicitly typed as strings, the result is as expected:

string s1 = "Test" + 123.ToString();
string s2 = "Test123";

bool check1 = s1 == s2; // True

Internally FluentValidation needs to be changed to use .Equals, and also should optionally accept an IEqualityComparer. To work around this for now, you can add your own test extension that takes a comparer:

public static class MyExtensions {
  public static IEnumerable<ValidationFailure> WithCustomState(this IEnumerable<ValidationFailure> failures, object expectedCustomState, IEqualityComparer comparer) {
	  return failures.When(failure => comparer.Equals(failure.CustomState, expectedCustomState), $"Expected custom state of '{expectedCustomState}'. Actual state was '{{State}}'");
  }
}

…which you can then use like this:

result.ShouldHaveValidationErrorFor(x => x.Surname).WithCustomState("Test123", StringComparer.Ordinal);

I’ll also ensure this is updated for a future version and I’ll post here once it’s done.

[JeremySkinner]

Implemented in 9.5.2