If we have a fixture whose methods take or return a class that is not one of the standard Slim types, we can add a simple custom type converter very easily, using the generic converter fitSharp.Slim.Operators.Converter.

using fitSharp.Slim.Operators;

public class MyCustomConverter: Converter<CustomClass> {

    protected override CustomClass Parse(string input) {
       return new CustomClass ... created from input string ...
    }

    protected override string Compose(CustomClass input) {
        return ... string representation of custom class ...
    }
}

Then we include our CustomConverter in the Suite Configuration File :

<?xml version="1.0" encoding="utf-8" ?>
<suiteConfig>
  <ApplicationUnderTest>
    <addAssembly>C:\mypath\myassembly.dll</addAssembly>
    <addNamespace>My.Namespace</addNamespace>
  </ApplicationUnderTest>
  
  <Slim.Operators>
    <add>MyCustomConverter</add>
  </Slim.Operators>
</suiteConfig>