Initialization

An extension often has to run code once before the first expectation is evaluated, e.g. to register a custom value formatter. Use a module initializer, which runs when your assembly is loaded and before any other code in it:

using System.Runtime.CompilerServices;
using aweXpect.Formatting;

namespace MyExtension
{
    internal static class MyExtensionInitializer
    {
        [ModuleInitializer]
        internal static void Initialize()
            => ValueFormatter.Register(new MyValueFormatter());
    }
}

A registered formatter applies process-wide, to all threads and async flows, until the returned IDisposable is disposed. When several registered formatters can format a value, the most recently registered one is used.

Older target frameworks

ModuleInitializerAttribute is a compiler feature requiring C# 9, not a specific target framework. Where it is missing (e.g. netstandard2.0 or net48), declare it as an internal type in your own package.