Faster & More Reliable Integration Testing Against Marten Projections or Subscriptions

I just pulled the trigger on Marten 8.8 and Wolverine 4.10 earlier today. Neither is particularly large, but there’s some new toys and an important improvement for test automation support that are worth calling out.

My goodness, that title is a mouthful. I’ve been helping a couple different JasperFx Software clients and community users on Discord with their test automation harnesses. In all cases, there was some complexity involved because of the usage of some mix of asynchronous projections or event subscriptions in Marten or asynchronous messaging with Wolverine. As part of that work to support a client today, Marten has this new trick (with a cameo from the related JasperFx Alba tool for HTTP service testing):

// This is bootstrapping the actual application using
// its implied Program.Main() set up
Host = await AlbaHost.For<Program>(b =>
{
    b.ConfigureServices((context, services) =>
    {
        // Important! You can make your test harness work a little faster (important on its own)
        // and probably be more reliable by overriding your Marten configuration to run all
        // async daemons in "Solo" mode so they spin up faster and there's no issues from
        // PostgreSQL having trouble with advisory locks when projections are rapidly started and stopped

        // This was added in V8.8
        services.MartenDaemonModeIsSolo();

        services.Configure<MartenSettings>(s =>
        {
            s.SchemaName = SchemaName;
        });
    });
});

Specifically note the new `IServiceCollection.MartenDaemonModeIsSolo()`. That is overriding any Marten async daemons that normally run with the “Hot/Cold” load distribution that is appropriate for production with Marten’s “Solo” load distribution so that your test harness can spin up much faster. In addition, this mode will enable Marten to more quickly shut down, then restart all asynchronous projections or subscriptions in tests when you use this existing testing helper to reset state:

        // OR if you use the async daemon in your tests, use this
        // instead to do the above, but also cleanly stop all projections,
        // reset the data, then start all async projections and subscriptions up again
        await Host.ResetAllMartenDataAsync();

In the above usage, that ResetAllMartenDataAsync() is smart enough to first disable all asynchronous projections and subscriptions, reset the Marten data store to your configured baseline state (effectively by wiping out all data, then reapplying all your “initial data”), then restarting all asynchronous projections and subscriptions from the new baseline.

Having the “Solo” load distribution will make the constant teardown and restart of the asynchronous projections faster than it would with a “Hot/Cold” configuration where Marten still assumes there might be other nodes running.

If you or your shop would want some assistance with test automation using the Critter Stack or otherwise, drop me a note at jeremy@jasperfx.net and I can chat about what we could do to help you out.

I’ll be discussing this new feature and quite a bit more in a live stream tomorrow (August 20th) at 2:00PM US Central time: