Microsoft.CodeAnalysis.Testing.DiagnosticResults has no option for valiadtion of the HelpURI

[smaillet]

Microsoft.CodeAnalysis.Testing.DiagnosticResults has no option for valiadtion of the HelpURI. It has a lot of WthXyZ for creating a value in tests, all of which are useful. However, it does not consider the HelpURI. This is a known problematic area that requires testing but there's no way to do that using DiagnosticResult.

[smaillet]

Amending this and updating the title to reflect the problem.
The problem is that the analyzer test library contains heuristics on validating a DiagnosticResult that is NOT documented. The rules of comparison are not known and expectations/assumptions are, apparently, not in such an implementation. For example:

analyzerTest.ExpectedDiagnostics.AddRange(
   [
       new DiagnosticResult("FOO004", DiagnosticSeverity.Warning)
          .WithSpan(9, 6, 9, 127)
          .WithArguments("foo", "bar"), // Not verified! Generator could use any incorrect value
   ]
 );

await analyzerTest.RunAsync( TestContext.CancellationToken );

Trying to find the implementation of this validation I've run into a large scale of not familiar with the code base and special conditions like using WithLocation(9,6) will match any diagnostic that has (9, 6) as the start, so not exactly value equality. It's more like a "good enough for government work" but does not define the rules it uses. Additionally, there's no way to test the help URI nor any diagnostic using WithArguments(). Basically, there's two things problematic here:

1. The heuristics aren't known/documented
2. There's no way to verify anything not included in the heuristics of the tests.