Integration testing an endpoint that executes a command

1-Command.cs

sealed record MyCommand(string Message) : ICommand;

sealed class MyCommandHandler : ICommandHandler<MyCommand>
{
    public Task ExecuteAsync(MyCommand command, CancellationToken ct)
        => Task.CompletedTask;
}

2-Endpoints.cs

sealed record MyRequest(string Msg);

[HttpGet("/endpoint"), AllowAnonymous]
sealed class MyEndpoint : Endpoint<MyRequest>
{
    public override async Task HandleAsync(MyRequest r, CancellationToken c)
    {
        var cmd = new MyCommand(r.Msg);
        await cmd.ExecuteAsync(c); // "test command receiver" is used to determine if command was executed by the endpoint.
        await Send.OkAsync("all good!");
    }
}

3-AppFixture.cs

public class Sut : AppFixture<Program>
{
    protected override void ConfigureServices(IServiceCollection s)
    {
        s.RegisterTestCommandReceivers(); // register the test command receiver service
    }
}

4-Test.cs

public class MyTests(Sut App) : TestBase<Sut>
{
    [Fact]
    public async Task Endpoint_Executes_Correct_Command()
    {
        //obtain a "test command receiver" for you command type
        var receiver = App.Services.GetTestCommandReceiver<MyCommand>();

        //call the endpoint
        var (rsp, _) = await App.Client.GETAsync<MyEndpoint, MyRequest, EmptyResponse>(new("yello!"));
        rsp.IsSuccessStatusCode.ShouldBeTrue();

        //check if "test command receiver" received the command that's supposed to be executed by the endpoint.
        var received = await receiver.WaitForMatchAsync(e => e.Message == "yello!", timeoutSeconds: 3, ct: Cancellation);
        received.Any().ShouldBeTrue();
    }
}