Char Assertions

[thomhurst]

Discussed in #2314

^{Originally posted by AnnaSasDev May 2, 2025}
For a highly specific thing, whih might be better built differently but that is besides the point of this discussion, I wanted to do something like the folloing (tiny example):

char a = 'a'
await Assert.That(a).IsDigit()

But I didnt find any assertions for this already in TUnit, so I wanted to put out some feelers out if this is something that could be implemented? If so, I would love to work on it, and I would probably want to implement the ones that are direct takeovers from in the standard library on the char type, and their IsNot... variants:

• IsAscii
• IsAsciiDigit
• IsAsciiLetterLower
• IsAsciiLetterUpper
• IsAsciiLetterOrDigit
• IsAsciiHexDigit
• IsAsciiHexDigitUpper
• IsAsciiHexDigitLower
• IsDigit
• IsBetween
• IsLetter
• IsWhiteSpace
• IsUpper
• IsLower
• IsPunctuation
• IsLetterOrDigit
• IsControl
• IsNumber
• IsSeparator
• IsSurrogate
• IsSymbol
• IsHighSurrogate
• IsLowSurrogate

[thomhurst]

cc @AnnaSasDev

[AnnaSasDev]

I wonder if something like a generator couldnt do the bulk of the lifting for this, given I have just seen the other issue #2316 and #2318 where I could build a generator that would be used like the following (pseudo code):

[CreateAssertion(typeof(char), nameof(char.IsDigit), TypeOfAssertion.Is)]
public partial class CharIsExtensions{}

Which would generate something like (again pseudo)

public partial class CharIsExtensions{
   public static InvokableValueAssertionBuilder<char> IsDigit(this IValueSource<char> valueSource) {
        return valueSource.RegisterAssertion(new FuncValueAssertCondition<string, int>(0,
            (value, _, self) => {
                if (value is null) {
                    self.FailWithMessage("Actual char is null");
                    return false;
                }
                
                return value.IsDigit();
            },
            (s, _, _) => $"'{s}' was not a digit",
            $"to be digit")
            , []); }
}

and vice versa with a TypeOfAssertion.IsNot and maybe some extra params to make the return messages more verbose or not.

[thomhurst]

That sounds interesting! I wouldn't be opposed to that!

Sounds like a lot more work up-front, but would be good going forwards for easily asserting on more in-built types.

[AnnaSasDev]

That sounds interesting! I wouldn't be opposed to that!

Sounds like a lot more work up-front, but would be good going forwards for easily asserting on more in-built types.

How "early" of an early pr draft do you want me to make, because just having tinkered with it for a second I already realize it will require quite a lot of input as to where to place the required attributes, what the project name will be, etc...

[thomhurst]

Whenever ya like. Happy for a draft to be open whenever !

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